Installation of beam screens in LHC arc cryomagnets

CERN Document Server

Cruikshank, P; Schneider, G; Veness, R J M

1999-01-01

Beam screens will be installed in the cold bores of the LHC arc cryodipoles and Short Straight Sections (SSS). This note describes the constraints on the beam screen installation imposed by the beam vacuum interconnects and Beam Position Monitors (BPM), and explains the installation scenario which has been adopted.

Arc-based smoothing of ion beam intensity on targets

International Nuclear Information System (INIS)

Friedman, Alex

2012-01-01

By manipulating a set of ion beams upstream of a target, it is possible to arrange for a smoother deposition pattern, so as to achieve more uniform illumination of the target. A uniform energy deposition pattern is important for applications including ion-beam-driven high energy density physics and heavy-ion beam-driven inertial fusion energy (“heavy-ion fusion”). Here, we consider an approach to such smoothing that is based on rapidly “wobbling” each of the beams back and forth along a short arc-shaped path, via oscillating fields applied upstream of the final pulse compression. In this technique, uniformity is achieved in the time-averaged sense; this is sufficient provided the beam oscillation timescale is short relative to the hydrodynamic timescale of the target implosion. This work builds on two earlier concepts: elliptical beams applied to a distributed-radiator target [D. A. Callahan and M. Tabak, Phys. Plasmas 7, 2083 (2000)] and beams that are wobbled so as to trace a number of full rotations around a circular or elliptical path [R. C. Arnold et al., Nucl. Instrum. Methods 199, 557 (1982)]. Here, we describe the arc-based smoothing approach and compare it to results obtainable using an elliptical-beam prescription. In particular, we assess the potential of these approaches for minimization of azimuthal asymmetry, for the case of a ring of beams arranged on a cone. It is found that, for small numbers of beams on the ring, the arc-based smoothing approach offers superior uniformity. In contrast with the full-rotation approach, arc-based smoothing remains usable when the geometry precludes wobbling the beams around a full circle, e.g., for the X-target [E. Henestroza, B. G. Logan, and L. J. Perkins, Phys. Plasmas 18, 032702 (2011)] and some classes of distributed-radiator targets.

Configuration of the Beam Loss Monitors for the LHC arcs

CERN Document Server

Arauzo-Garcia, A

2000-01-01

A revised configuration for a beam loss detection system is given for the arcs of the LHC. The last modifications of the LHC arc layout have been taken into account, LHC optics version 6.2. A set of 6 Loss Detectors will be placed outside the cryostat around each short straight section. Quench alarm thresholds are estimated for each detector in all possible LHC arc layout configurations. Threshold values are proposed for top and injection energy beam loss.

SU-F-T-531: Determination of Site-Specific Dynamic-Jaw Versus Static-Jaw RapidArc Delivery

Energy Technology Data Exchange (ETDEWEB)

Tien, C [Community Hospital, Munster, IN (United States); Brewer, M [Franciscan St Margaret Health, Hammond, IN (United States); Studenski, M [University of Miami, Miami, FL (United States)

2016-06-15

Purpose: Dynamic-jaw tracking maximizes the area blocked by both jaw and MLC in RapidArc. We developed a method to quantify jaw tracking. Methods: An Eclipse Scripting API (ESAPI) was used to export beam parameters for each arc’s control points. The specific beam parameters extracted were: gantry angle, control point number, meterset, x-jaw positions, y-jaw positions, MLC bank-number, MLC leaf-number, and MLC leaf-position. Each arc contained 178 control points with 120 MLC positions. MATLAB routines were written to process these parameters in order to calculate both the beam aperture (unblocked) size for each control point. An average aperture size was weighted by meterset. Jaw factor was defined as the ratio between dynamic-jaw to static-jaw aperture size. Jaw factor was determined for forty retrospectively replanned patients treated with static-jaw delivery sites including lung, brain, prostate, H&N, rectum, and bladder. Results: Most patients had multiple arcs and reduced-field boosts, resulting in 151 fields. Of these, the lowest (0.4722) and highest (0.9622) jaw factor was observed in prostate and rectal cases, respectively. The median jaw factor was 0.7917 meaning there is the potential unincreased blocking by 20%. Clinically, the dynamic-jaw tracking represents an area surrounding the target which would receive MLC-only leakage transmission of 1.68% versus 0.1% with jaws. Jaw-tracking was more pronounced at areas farther from the target. In prostate patients, the rectum and bladder had 5.5% and 6.3% lower mean dose, respectively; the structures closer to the prostate such as the rectum and bladder both had 1.4% lower mean dose. Conclusion: A custom ESAPI script was coupled with a MATLAB routine in order to extract beam parameters from static-jaw plans and their replanned dynamic-jaw deliveries. The effects were quantified using jaw factor which is the ratio between the meterset weighted aperture size for dynamic-jaw fields versus static-jaw fields.

Application of the electron pencil beam redefinition algorithm to electron arc therapy

International Nuclear Information System (INIS)

Chi, P.-C.M.; Hogstrom, Kenneth R.; Starkschall, George; Boyd, Robert A.; Tucker, Susan L.; Antolak, John A.

2006-01-01

This project investigated the potential of summing fixed-beam dose distributions calculated using the pencil-beam redefinition algorithm (PBRA) at small angular steps (1 deg.) to model an electron arc therapy beam. The PRBA, previously modified to model skin collimation, was modified further by incorporating two correction factors. One correction factor that is energy, SSD (source-to-surface distance), and field-width dependent constrained the calculated dose output to be the same as the measured dose output for fixed-beam geometries within the range of field widths and SSDs encountered in arc therapy. Another correction factor (single field-width correction factor for each energy) compensated for large-angle scattering not being modeled, allowing a more accurate calculation of dose output at mid arc. The PBRA was commissioned to accurately calculate dose in a water phantom for fixed-beam geometries typical of electron arc therapy. Calculated central-axis depth doses agreed with measured doses to within 2% in the low-dose gradient regions and within 1-mm in the high-dose gradient regions. Off-axis doses agreed to within 2 mm in the high-dose gradient regions and within 3% in the low-dose gradient regions. Arced-beam calculations of dose output and depth dose at mid arc were evaluated by comparing to data measured using two cylindrical water phantoms with radii of 12 and 15 cm at 10 and 15 MeV. Dose output was measured for all combinations of phantom radii of curvature, collimator widths (4, 5, and 6 cm), and arc angles (0 deg., 20 deg., 40 deg., 60 deg., 80 deg., and 90 deg.) for both beam energies. Results showed the calculated mid-arc dose output to agree within 2% of measurement for all combinations. For a 90 deg.arc angle and 5x20 cm 2 field size, the calculated mid-arc depth dose in the low-dose gradient region agreed to within 2% of measurement for all depths at 10 MeV and for depths greater than depth of dose maximum R 100 at 15 MeV. For depths in the

Poster - 42: TB - ARC: A Total Body photon ARC technique using a commercially available linac

Energy Technology Data Exchange (ETDEWEB)

Evans, Michael D. C.; Ruo, Russell; Patrocinio, Horacio J.; Poon, Emily; Freeman, Carolyn; Hijal, Tarek; Parker, William [McGill University Health Centre (Canada)

2016-08-15

We have developed a total body photon irradiation technique using multiple overlapping open field arcs (TB-ARC). This simple technique uses predetermined arc-weights, with MUs calculated as a function of prescription depth only. Patients lie on a stretcher, in the prone/supine treatment position with AP/PA arcs. This treatment position has many advantages including ease of delivery (especially for tall, pediatric or compromised patients), dose uniformity, simplicity for organ shielding, and imaging capabilities. Using a Varian TrueBeam linac, 14 arcs using 40×40 cm{sup 2} 6 MV open photon beams, sweeping across 10 degrees each, complete a 140 degree arc. The nominal SSD at zero degrees is 200 cm. Arcs at the sweep limits (+/− 70 degrees) are differentially weighted and deliver a dose within 10% of the prescription on central axis, at a depth of 10 cm over a superior-inferior length of 275 cm. CT planning using Varian Eclipse enables dose evaluation. A custom made beam spoiler, consisting of a 2.5 m sheet of polycarbonate (6 mm thick) increases the surface dose from 45% to 90%. This beam spoiler also serves as a support in the event that differential attenuation is required for organs such as lung, heart, liver, kidneys. The geometry of the sweeping beam technique limits organ dose (using varying thicknesses of melting alloy) to about 20% and 40% of prescription at dmax and midplane respectively. Digital imaging with a portable DR cassette enables proper attenuator location prior to treatment.

A novel method for sub-arc VMAT dose delivery verification based on portal dosimetry with an EPID.

Science.gov (United States)

Cools, Ruud A M; Dirkx, Maarten L P; Heijmen, Ben J M

2017-11-01

The EPID-based sub-arc verification of VMAT dose delivery requires synchronization of the acquired electronic portal images (EPIs) with the VMAT delivery, that is, establishment of the start- and stop-MU of the acquired images. To realize this, published synchronization methods propose the use of logging features of the linac or dedicated hardware solutions. In this study, we developed a novel, software-based synchronization method that only uses information inherently available in the acquired images. The EPIs are continuously acquired during pretreatment VMAT delivery and converted into Portal Dose Images (PDIs). Sub-arcs of approximately 10 MU are then defined by combining groups of sequentially acquired PDIs. The start- and stop-MUs of measured sub-arcs are established in a synchronization procedure, using only dosimetric information in measured and predicted PDIs. Sub-arc verification of a VMAT dose delivery is based on comparison of measured sub-arc PDIs with synchronized, predicted sub-arc PDIs, using γ-analyses. To assess the accuracy of this new method, measured and predicted PDIs were compared for 20 clinically applied VMAT prostate cancer plans. The sensitivity of the method for detection of delivery errors was investigated using VMAT deliveries with intentionally inserted, small perturbations (25 error scenarios; leaf gap deviations ≤ 1.5 mm, leaf motion stops during ≤ 15 MU, linac output error ≤ 2%). For the 20 plans, the average failed pixel rates (FPR) for full-arc and sub-arc dose QA were 0.36% ± 0.26% (1 SD) and 0.64% ± 0.88%, based on 2%/2 mm and 3%/3 mm γ-analyses, respectively. Small systematic perturbations of up to 1% output error and 1 mm leaf offset were detected using full-arc QA. Sub-arc QA was able to detect positioning errors in three leaves only during approximately 20 MU and small dose delivery errors during approximately 40 MU. In an ROC analysis, the area under the curve (AUC) for the combined full-arc/sub-arc approach was

Aperture modulated arc therapy

International Nuclear Information System (INIS)

Crooks, S M; Wu, Xiaodong; Takita, C; Watzich, M; Xing Lei

2003-01-01

We show that it is possible to translate an intensity modulated radiation therapy (IMRT) treatment plan and deliver it as a single arc. This technique is referred to in this paper as aperture modulation arc therapy (AMAT). During this arc, the MLC leaves do not conform to the projection of the target PTV and the machine output of the accelerator has a constant value. Dose was calculated using the CORVUS 4.0 IMRT system, which uses a pencil beam dose algorithm, and treatments were delivered using a Varian 2100C/D Clinac. Results are presented for a head and neck and a prostate case, showing the equivalence of the IMRT and the translated AMAT delivery. For a prostate AMAT delivery, coronal plane film dose for the IMRT and AMAT deliveries agreed within 7.19 ± 6.62%. For a meningioma the coronal plane dose distributions were similar to a value of 4.6 ± 6.62%. Dose to the isocentre was measured as being within 2% of the planned value in both cases

Volumetric Modulated Arc Therapy for Spine Radiosurgery: Superior Treatment Planning and Delivery Compared to Static Beam Intensity Modulated Radiotherapy.

Science.gov (United States)

Zach, Leor; Tsvang, Lev; Alezra, Dror; Ben Ayun, Maoz; Harel, Ran

2016-01-01

Spine stereotactic radiosurgery (SRS) delivers an accurate and efficient high radiation dose to vertebral metastases in 1-5 fractions. We aimed to compare volumetric modulated arc therapy (VMAT) to static beam intensity modulated radiotherapy (IMRT) for spine SRS. Ten spine lesions of previously treated SRS patients were planned retrospectively using both IMRT and VMAT with a prescribed dose of 16 Gy to 100% of the planning target volume (PTV). The plans were compared for conformity, homogeneity, treatment delivery time, and safety (spinal cord dose). All evaluated parameters favored the VMAT plan over the IMRT plans. D min in the IMRT was significantly lower than in the VMAT plan (7.65 Gy/10.88 Gy, p DSC) was found to be significantly better for the VMAT plans compared to the IMRT plans (0.77/0.58, resp., p  value < 0.01), and an almost 50% reduction in the net treatment time was calculated for the VMAT compared to the IMRT plans (6.73 min/12.96 min, p < 0.001). In our report, VMAT provides better conformity, homogeneity, and safety profile. The shorter treatment time is a major advantage and not only provides convenience to the painful patient but also contributes to the precision of this high dose radiation therapy.

Delivery quality assurance with ArcCHECK

International Nuclear Information System (INIS)

Neilson, Christopher; Klein, Michael; Barnett, Rob; Yartsev, Slav

2013-01-01

Radiation therapy requires delivery quality assurance (DQA) to ensure that treatment is accurate and closely follows the plan. We report our experience with the ArcCHECK phantom and investigate its potential optimization for the DQA process. One-hundred seventy DQA plans from 84 patients were studied. Plans were classified into 2 groups: those with the target situated on the diodes of the ArcCHECK (D plans) and those with the target situated at the center (C plans). Gamma pass rates for 8 target sites were examined. The parameters used to analyze the data included 3%/3 mm with the Van Dyk percent difference criteria (VD) on, 3%/3 mm with the VD off, 2%/2 mm with the VD on, and x/3 mm with the VD on and the percentage dosimetric agreement “x” for diode plans adjusted. D plans typically displayed maximum planned dose (MPD) on the cylindrical surface containing ArcCHECK diodes than center plans, resulting in inflated gamma pass rates. When this was taken into account by adjusting the percentage dosimetric agreement, C plans outperformed D plans by an average of 3.5%. ArcCHECK can streamline the DQA process, consuming less time and resources than radiographic films. It is unnecessary to generate 2 DQA plans for each patient; a single center plan will suffice. Six of 8 target sites consistently displayed pass rates well within our acceptance criteria; the lesser performance of head and neck and spinal sites can be attributed to marginally lower doses and increased high gradient of plans

Dual-gated volumetric modulated arc therapy

International Nuclear Information System (INIS)

Fahimian, Benjamin; Wu, Junqing; Wu, Huanmei; Geneser, Sarah; Xing, Lei

2014-01-01

Gated Volumetric Modulated Arc Therapy (VMAT) is an emerging radiation therapy modality for treatment of tumors affected by respiratory motion. However, gating significantly prolongs the treatment time, as delivery is only activated during a single respiratory phase. To enhance the efficiency of gated VMAT delivery, a novel dual-gated VMAT (DG-VMAT) technique, in which delivery is executed at both exhale and inhale phases in a given arc rotation, is developed and experimentally evaluated. Arc delivery at two phases is realized by sequentially interleaving control points consisting of MUs, MLC sequences, and angles of VMAT plans generated at the exhale and inhale phases. Dual-gated delivery is initiated when a respiration gating signal enters the exhale window; when the exhale delivery concludes, the beam turns off and the gantry rolls back to the starting position for the inhale window. The process is then repeated until both inhale and exhale arcs are fully delivered. DG-VMAT plan delivery accuracy was assessed using a pinpoint chamber and diode array phantom undergoing programmed motion. DG-VMAT delivery was experimentally implemented through custom XML scripting in Varian’s TrueBeam™ STx Developer Mode. Relative to single gated delivery at exhale, the treatment time was improved by 95.5% for a sinusoidal breathing pattern. The pinpoint chamber dose measurement agreed with the calculated dose within 0.7%. For the DG-VMAT delivery, 97.5% of the diode array measurements passed the 3%/3 mm gamma criterion. The feasibility of DG-VMAT delivery scheme has been experimentally demonstrated for the first time. By leveraging the stability and natural pauses that occur at end-inspiration and end-exhalation, DG-VMAT provides a practical method for enhancing gated delivery efficiency by up to a factor of two

Utilization of an arc-heated jet for production of supersonic seeded beams of atomic nitrogen

International Nuclear Information System (INIS)

Bickes, R.W. Jr.; Newton, K.R.; Herrmann, J.M.; Bernstein, R.B.

1976-01-01

Intense supersonic beams of atomic nitrogen (>10 17 atoms sr -1 sec -1 ) have been produced from the dissociation of N 2 in an Ar arc (at temperatures in excess of 6000 K) using the arc-heated nozzle beam source of Young, Rodgers, and Knuth. Experiments characterizing the N 2 dissociation and the translational energies of the N, N 2 , and Ar components in the beams are described. Evidence is presented for the formation of atomic C as well as C 2 and CH from the pyrolysis of CH 4 and C 2 H 4 in the Ar arc

Volumetric Modulated Arc Therapy for Spine Radiosurgery: Superior Treatment Planning and Delivery Compared to Static Beam Intensity Modulated Radiotherapy

Directory of Open Access Journals (Sweden)

Leor Zach

2016-01-01

Full Text Available Purpose. Spine stereotactic radiosurgery (SRS delivers an accurate and efficient high radiation dose to vertebral metastases in 1–5 fractions. We aimed to compare volumetric modulated arc therapy (VMAT to static beam intensity modulated radiotherapy (IMRT for spine SRS. Methods and Materials. Ten spine lesions of previously treated SRS patients were planned retrospectively using both IMRT and VMAT with a prescribed dose of 16 Gy to 100% of the planning target volume (PTV. The plans were compared for conformity, homogeneity, treatment delivery time, and safety (spinal cord dose. Results. All evaluated parameters favored the VMAT plan over the IMRT plans. Dmin in the IMRT was significantly lower than in the VMAT plan (7.65 Gy/10.88 Gy, p<0.001, the Dice Similarity Coefficient (DSC was found to be significantly better for the VMAT plans compared to the IMRT plans (0.77/0.58, resp., p  value<0.01, and an almost 50% reduction in the net treatment time was calculated for the VMAT compared to the IMRT plans (6.73 min/12.96 min, p<0.001. Conclusions. In our report, VMAT provides better conformity, homogeneity, and safety profile. The shorter treatment time is a major advantage and not only provides convenience to the painful patient but also contributes to the precision of this high dose radiation therapy.

Optimal partial-arcs in VMAT treatment planning

International Nuclear Information System (INIS)

Wala, Jeremiah; Salari, Ehsan; Chen Wei; Craft, David

2012-01-01

We present a method for improving the delivery efficiency of VMAT by extending the recently published VMAT treatment planning algorithm vmerge to automatically generate optimal partial-arc plans. A high-quality initial plan is created by solving a convex multicriteria optimization problem using 180 equi-spaced beams. This initial plan is used to form a set of dose constraints, and a set of partial-arc plans is created by searching the space of all possible partial-arc plans that satisfy these constraints. For each partial-arc, an iterative fluence map merging and sequencing algorithm (vmerge) is used to improve the delivery efficiency. Merging continues as long as the dose quality is maintained above a user-defined threshold. The final plan is selected as the partial-arc with the lowest treatment time. The complete algorithm is called pmerge. Partial-arc plans are created using pmerge for a lung, liver and prostate case, with final treatment times of 127, 245 and 147 s. Treatment times using full arcs with vmerge are 211, 357 and 178 s. The mean doses to the critical structures for the vmerge and pmerge plans are kept within 5% of those in the initial plan, and the target volume covered by the prescription isodose is maintained above 98% for the pmerge and vmerge plans. Additionally, we find that the angular distribution of fluence in the initial plans is predictive of the start and end angles of the optimal partial-arc. We conclude that VMAT delivery efficiency can be improved by employing partial-arcs without compromising dose quality, and that partial-arcs are most applicable to cases with non-centralized targets. (paper)

Excimer laser beam delivery systems for medical applications

Science.gov (United States)

Kubo, Uichi; Hashishin, Yuichi; Okada, Kazuyuki; Tanaka, Hiroyuki

1993-05-01

We have been doing the basic experiments of UV laser beams and biotissue interaction with both KrF and XeCl lasers. However, the conventional optical fiber can not be available for power UV beams. So we have been investigating about UV power beam delivery systems. These experiments carry on with the same elements doped quartz fibers and the hollow tube. The doped elements are OH ion, chlorine and fluorine. In our latest work, we have tried ArF excimer laser and biotissue interactions, and the beam delivery experiments. From our experimental results, we found that the ArF laser beam has high incision ability for hard biotissue. For example, in the case of the cow's bone incision, the incision depth by ArF laser was ca.15 times of KrF laser. Therefore, ArF laser would be expected to harden biotissue therapy as non-thermal method. However, its beam delivery is difficult to work in this time. We will develop ArF laser beam delivery systems.

SU-F-P-39: End-To-End Validation of a 6 MV High Dose Rate Photon Beam, Configured for Eclipse AAA Algorithm Using Golden Beam Data, for SBRT Treatments Using RapidArc

Energy Technology Data Exchange (ETDEWEB)

Ferreyra, M; Salinas Aranda, F; Dodat, D; Sansogne, R; Arbiser, S [Vidt Centro Medico, Ciudad Autonoma De Buenos Aires, Ciudad Autonoma de Buenos Aire (Argentina)

2016-06-15

Purpose: To use end-to-end testing to validate a 6 MV high dose rate photon beam, configured for Eclipse AAA algorithm using Golden Beam Data (GBD), for SBRT treatments using RapidArc. Methods: Beam data was configured for Varian Eclipse AAA algorithm using the GBD provided by the vendor. Transverse and diagonals dose profiles, PDDs and output factors down to a field size of 2×2 cm2 were measured on a Varian Trilogy Linac and compared with GBD library using 2% 2mm 1D gamma analysis. The MLC transmission factor and dosimetric leaf gap were determined to characterize the MLC in Eclipse. Mechanical and dosimetric tests were performed combining different gantry rotation speeds, dose rates and leaf speeds to evaluate the delivery system performance according to VMAT accuracy requirements. An end-to-end test was implemented planning several SBRT RapidArc treatments on a CIRS 002LFC IMRT Thorax Phantom. The CT scanner calibration curve was acquired and loaded in Eclipse. PTW 31013 ionization chamber was used with Keithley 35617EBS electrometer for absolute point dose measurements in water and lung equivalent inserts. TPS calculated planar dose distributions were compared to those measured using EPID and MapCheck, as an independent verification method. Results were evaluated with gamma criteria of 2% dose difference and 2mm DTA for 95% of points. Results: GBD set vs. measured data passed 2% 2mm 1D gamma analysis even for small fields. Machine performance tests show results are independent of machine delivery configuration, as expected. Absolute point dosimetry comparison resulted within 4% for the worst case scenario in lung. Over 97% of the points evaluated in dose distributions passed gamma index analysis. Conclusion: Eclipse AAA algorithm configuration of the 6 MV high dose rate photon beam using GBD proved efficient. End-to-end test dose calculation results indicate it can be used clinically for SBRT using RapidArc.

Resistive-wall Wake Effect in the Beam Delivery System

International Nuclear Information System (INIS)

Delayen, J.R.; Jefferson Lab; Wu, Juhao; Raubenheimer, T.O.; SLAC; Wang, Jiunn-Ming; BNL, NSLS

2005-01-01

General formulae for resistive-wall induced beam dilution are presented and then applied to the final beam delivery system of linear colliders. Criteria for the design of final beam delivery systems are discussed

Dosimetric Impact of the Interplay Effect During Stereotactic Lung Radiation Therapy Delivery Using Flattening Filter-Free Beams and Volumetric Modulated Arc Therapy

International Nuclear Information System (INIS)

Ong, Chin Loon; Dahele, Max; Slotman, Ben J.; Verbakel, Wilko F.A.R.

2013-01-01

Purpose: We investigated the dosimetric impact of the interplay effect during RapidArc stereotactic body radiation therapy for lung tumors using flattening filter-free (FFF) beams with different dose rates. Methods and Materials: Seven tumors with motion ≤20 mm, treated with 10-MV FFF RapidArc, were analyzed. A programmable phantom with sinusoidal longitudinal motion (30-mm diameter “tumor” insert; period = 5 s; individualized amplitude from planning 4-dimensional computed tomography) was used for dynamic dose measurements. Measurements were made with GafChromic EBT III films. Plans delivered the prescribed dose to 95% of the planning target volume, created by a 5-mm expansion of the internal target volume. They comprised 2 arcs and maximum dose rates of 400 and 2400 MU/min. For 2400 MU/min plans, measurements were repeated at 3 different initial breathing phases to model interplay over 2 to 3 fractions. For 3 cases, 2 extra plans were created using 1 full rotational arc (with contralateral lung avoidance sector) and 1 partial arc of 224° to 244°. Dynamic and convolved static measurements were compared by use of gamma analysis of 3% dose difference and 1 mm distance-to-agreement. Results: For 2-arc 2400 MU/min plans, maximum dose deviation of 9.4% was found in a single arc; 7.4% for 2 arcs (single fraction) and 99% of the area within the region of interest passed the gamma criteria when all 3 measurements with different initial phases were combined. Single-fraction single-arc plans showed higher dose deviations, which diminished when dose distributions were summed over 2 fractions. All 400 MU/min plans showed good agreement in a single fraction measurement. Conclusion: Under phantom conditions, single-arc and single-fraction 2400 MU/min FFF RapidArc lung stereotactic body radiation therapy is susceptible to interplay. Two arcs and ≥2 fractions reduced the effect to a level that appeared unlikely to be clinically significant

SU-E-T-539: Fixed Versus Variable Optimization Points in Combined-Mode Modulated Arc Therapy Planning

International Nuclear Information System (INIS)

Kainz, K; Prah, D; Ahunbay, E; Li, X

2014-01-01

Purpose: A novel modulated arc therapy technique, mARC, enables superposition of step-and-shoot IMRT segments upon a subset of the optimization points (OPs) of a continuous-arc delivery. We compare two approaches to mARC planning: one with the number of OPs fixed throughout optimization, and another where the planning system determines the number of OPs in the final plan, subject to an upper limit defined at the outset. Methods: Fixed-OP mARC planning was performed for representative cases using Panther v. 5.01 (Prowess, Inc.), while variable-OP mARC planning used Monaco v. 5.00 (Elekta, Inc.). All Monaco planning used an upper limit of 91 OPs; those OPs with minimal MU were removed during optimization. Plans were delivered, and delivery times recorded, on a Siemens Artiste accelerator using a flat 6MV beam with 300 MU/min rate. Dose distributions measured using ArcCheck (Sun Nuclear Corporation, Inc.) were compared with the plan calculation; the two were deemed consistent if they agreed to within 3.5% in absolute dose and 3.5 mm in distance-to-agreement among > 95% of the diodes within the direct beam. Results: Example cases included a prostate and a head-and-neck planned with a single arc and fraction doses of 1.8 and 2.0 Gy, respectively. Aside from slightly more uniform target dose for the variable-OP plans, the DVHs for the two techniques were similar. For the fixed-OP technique, the number of OPs was 38 and 39, and the delivery time was 228 and 259 seconds, respectively, for the prostate and head-and-neck cases. For the final variable-OP plans, there were 91 and 85 OPs, and the delivery time was 296 and 440 seconds, correspondingly longer than for fixed-OP. Conclusion: For mARC, both the fixed-OP and variable-OP approaches produced comparable-quality plans whose delivery was successfully verified. To keep delivery time per fraction short, a fixed-OP planning approach is preferred

SU-E-T-539: Fixed Versus Variable Optimization Points in Combined-Mode Modulated Arc Therapy Planning

Energy Technology Data Exchange (ETDEWEB)

Kainz, K; Prah, D; Ahunbay, E; Li, X [Medical College of Wisconsin, Milwaukee, WI (United States)

2014-06-01

Purpose: A novel modulated arc therapy technique, mARC, enables superposition of step-and-shoot IMRT segments upon a subset of the optimization points (OPs) of a continuous-arc delivery. We compare two approaches to mARC planning: one with the number of OPs fixed throughout optimization, and another where the planning system determines the number of OPs in the final plan, subject to an upper limit defined at the outset. Methods: Fixed-OP mARC planning was performed for representative cases using Panther v. 5.01 (Prowess, Inc.), while variable-OP mARC planning used Monaco v. 5.00 (Elekta, Inc.). All Monaco planning used an upper limit of 91 OPs; those OPs with minimal MU were removed during optimization. Plans were delivered, and delivery times recorded, on a Siemens Artiste accelerator using a flat 6MV beam with 300 MU/min rate. Dose distributions measured using ArcCheck (Sun Nuclear Corporation, Inc.) were compared with the plan calculation; the two were deemed consistent if they agreed to within 3.5% in absolute dose and 3.5 mm in distance-to-agreement among > 95% of the diodes within the direct beam. Results: Example cases included a prostate and a head-and-neck planned with a single arc and fraction doses of 1.8 and 2.0 Gy, respectively. Aside from slightly more uniform target dose for the variable-OP plans, the DVHs for the two techniques were similar. For the fixed-OP technique, the number of OPs was 38 and 39, and the delivery time was 228 and 259 seconds, respectively, for the prostate and head-and-neck cases. For the final variable-OP plans, there were 91 and 85 OPs, and the delivery time was 296 and 440 seconds, correspondingly longer than for fixed-OP. Conclusion: For mARC, both the fixed-OP and variable-OP approaches produced comparable-quality plans whose delivery was successfully verified. To keep delivery time per fraction short, a fixed-OP planning approach is preferred.

TH-C-12A-09: Planning and Delivery of the Fully Dynamic Trajectory Modulated Arc Therapy: Application to Accelerated Partial Breast Irradiation

International Nuclear Information System (INIS)

Liang, J; Atwood, T; Fahimian, B; Chin, E; Hristov, D; Otto, K

2014-01-01

Purpose: A novel trajectory modulated arc therapy (TMAT) system was developed that uses source motion trajectory involving synchronized gantry rotation with translational and rotational couch movement. MLC motion and dose rate were fully optimized for dynamic beam delivery. This work presents a platform for planning deliverable TMAT on a collision free coronal trajectory and evaluates its benefit for accelerated partial breast irradiation (APBI) in a prone position. Methods: The TMAT algorithm was built on VMAT with modifications (physical properties on couch movement were defined) and enhancements (pencil beam dose calculation engine to support extended SSDs) to make it feasible for TMAT delivery. A Matlab software environment for TMAT optimization and dose calculation was created to allow any user specified motion axis. TMAT delivery was implemented on Varian TrueBeamTM STx via XML scripts. 10 prone breast irradiation cases were evaluated in VMAT and compared with a 6- field non-coplanar IMRT plan. Patient selection/exclusion criteria and structure contouring followed the guidelines of NSABP B-39/RTOG 0413 protocol. Results: TMAT delivery time was ∼4.5 minutes. 251.5°±7.88° of non-isocentric couch arc was achieved by the optimized trajectory with 180– 210 control points at 1°–2° couch increments. The improved dose distribution by TMAT was most clearly observed by the marked reduction in the volume of irradiated normal breast tissue in the high dose region. The ratios of the normal breast tissue volume receiving more than 50%, 80% and 100% of the prescription dose for TMAT versus IMRT were: V50%(TMAT/IMRT) = 78.38%±13.03%, V80%(TMAT/IMRT) = 44.19%±9.04% and V100% (TMAT/IMRT) = 9.96%±7.55%, all p≤0.01. Conclusion: The study is the first demonstration of planning and delivery implementation of a fully dynamic APBI TMAT system with continuous couch motion. TMAT achieved significantly improved dosimetry over noncoplanar IMRT on dose volume parameters

TH-C-12A-09: Planning and Delivery of the Fully Dynamic Trajectory Modulated Arc Therapy: Application to Accelerated Partial Breast Irradiation

Energy Technology Data Exchange (ETDEWEB)

Liang, J; Atwood, T; Fahimian, B; Chin, E; Hristov, D [Department of Radiation Oncology, Stanford University, CA (United States); Otto, K [Department of Physics, University of British Columbia, BC (Canada)

2014-06-15

Purpose: A novel trajectory modulated arc therapy (TMAT) system was developed that uses source motion trajectory involving synchronized gantry rotation with translational and rotational couch movement. MLC motion and dose rate were fully optimized for dynamic beam delivery. This work presents a platform for planning deliverable TMAT on a collision free coronal trajectory and evaluates its benefit for accelerated partial breast irradiation (APBI) in a prone position. Methods: The TMAT algorithm was built on VMAT with modifications (physical properties on couch movement were defined) and enhancements (pencil beam dose calculation engine to support extended SSDs) to make it feasible for TMAT delivery. A Matlab software environment for TMAT optimization and dose calculation was created to allow any user specified motion axis. TMAT delivery was implemented on Varian TrueBeamTM STx via XML scripts. 10 prone breast irradiation cases were evaluated in VMAT and compared with a 6- field non-coplanar IMRT plan. Patient selection/exclusion criteria and structure contouring followed the guidelines of NSABP B-39/RTOG 0413 protocol. Results: TMAT delivery time was ∼4.5 minutes. 251.5°±7.88° of non-isocentric couch arc was achieved by the optimized trajectory with 180– 210 control points at 1°–2° couch increments. The improved dose distribution by TMAT was most clearly observed by the marked reduction in the volume of irradiated normal breast tissue in the high dose region. The ratios of the normal breast tissue volume receiving more than 50%, 80% and 100% of the prescription dose for TMAT versus IMRT were: V50%(TMAT/IMRT) = 78.38%±13.03%, V80%(TMAT/IMRT) = 44.19%±9.04% and V100% (TMAT/IMRT) = 9.96%±7.55%, all p≤0.01. Conclusion: The study is the first demonstration of planning and delivery implementation of a fully dynamic APBI TMAT system with continuous couch motion. TMAT achieved significantly improved dosimetry over noncoplanar IMRT on dose volume parameters

Increasing of charge of uranium ion beam in vacuum-arc-type source (MEVVA)

CERN Document Server

Kulevoj, T V; Petrenko, S V; Seleznev, D N; Pershin, V I; Batalin, V A; Kolomiets, A A

2002-01-01

Research efforts with MEVVA type source (Metal Vapor Vacuum Arc) and with its modifications are in progress now in the ITEP. In the course of research one revealed possibility to increase charge state of generated beam of uranium ions. Increase of charge results from propagation of high-current vacuum-arc charge from the source cathode to the extra anode located in increasing axial magnetic field. One obtained uranium ion beam with 150 mA output current 10% of which were contributed by U sup 7 sup + uranium ions

A planning and delivery study of a rotational IMRT technique with burst delivery

International Nuclear Information System (INIS)

Kainz, Kristofer; Chen, Guang-Pei; Chang, Yu-Wen; Prah, Douglas; Sharon Qi, X.; Shukla, Himanshu P.; Stahl, Johannes; Allen Li, X.

2011-01-01

Purpose: A novel rotational IMRT (rIMRT) technique using burst delivery (continuous gantry rotation with beam off during MLC repositioning) is investigated. The authors evaluate the plan quality and delivery efficiency and accuracy of this dynamic technique with a conventional flat 6 MV photon beam. Methods: Burst-delivery rIMRT was implemented in a planning system and delivered with a 160-MLC linac. Ten rIMRT plans were generated for five anonymized patient cases encompassing head and neck, brain, prostate, and prone breast. All plans were analyzed retrospectively and not used for treatment. Among the varied plan parameters were the number of optimization points, number of arcs, gantry speed, and gantry angle range (alpha) over which the beam is turned on at each optimization point. Combined rotational/step-and-shoot rIMRT plans were also created by superimposing multiple-segment static fields at several optimization points. The rIMRT trial plans were compared with each other and with plans generated using helical tomotherapy and VMAT. Burst-mode rotational IMRT plans were delivered and verified using a diode array, ionization chambers, thermoluminescent dosimeters, and film. Results: Burst-mode rIMRT can achieve plan quality comparable to helical tomotherapy, while the former may lead to slightly better OAR sparing for certain cases and the latter generally achieves slightly lower hot spots. Few instances were found in which increasing the number of optimization points above 36, or superimposing step-and-shoot IMRT segments, led to statistically significant improvements in OAR sparing. Using an additional rIMRT partial arc yielded substantial OAR dose improvements for the brain case. Measured doses from the rIMRT plan delivery were within 4% of the plan calculation in low dose gradient regions. Delivery time range was 228-375 s for single-arc rIMRT 200-cGy prescription with a 300 MU/min dose rate, comparable to tomotherapy and VMAT. Conclusions: Rotational IMRT

Sci—Sat AM: Stereo — 08: Stereotactic Ablative Radiotherapy (SABR) for low, intermediate and high risk prostate cancer using Volumetric Modulated Arc Therapy (VMAT) with a 10x Flattening Filter Free (FFF) beam

International Nuclear Information System (INIS)

Mestrovic, A; Fortin, D; Alexander, A

2014-01-01

Purpose: To determine the feasibility of using Volumetric Modulated Arc Therapy (VMAT) with a 10x Flattening Filter Free (FFF) beam for Stereotactic Ablative Radiotherapy (SABR) for low, intermediate and high risk prostate cancer. Methods and Materials: Ten anonymized patient CT data sets were used in this planning study. For each patient CT data set, three sets of contours were generated: 1) low risk, 2) intermediate risk, and 3) high risk scenarios. For each scenario, a single-arc and a double-arc VMAT treatment plans were created. Plans were generated with the Varian Eclipse™ treatment planning system for a Varian TrueBeam™ linac equipped with Millenium 120 MLC. Plans were created using a 10x-FFF beam with a maximum dose rate of 2400 MU/min. Dose prescription was 36.25Gy/5 fractions with the planning objective of covering 99% of the Planning Target Volume with the 95% of the prescription dose. Normal tissue constraints were based on provincial prostate SABR planning guidelines, derived from national and international prostate SABR protocols. Plans were evaluated and compared in terms of: 1) dosimetric plan quality, and 2) treatment delivery efficiency. Results: Both single-arc and double-arc VMAT plans were able to meet the planning goals for low, intermediate and high risk scenarios. No significant dosimetric differences were observed between the plans. However, the treatment time was significantly lower for a single-arc VMAT plans. Conclusions: Prostate SABR treatments are feasible with 10x-FFF VMAT technique. A single-arc VMAT offers equivalent dosimetric plan quality and a superior treatment delivery efficiency, compared to a double-arc VMAT

Beam's-Eye-View Dosimetrics-Guided Inverse Planning for Aperture-Modulated Arc Therapy

International Nuclear Information System (INIS)

Ma Yunzhi; Popple, Richard; Suh, Tae-Suk; Xing Lei

2009-01-01

Purpose: To use angular beam's-eye-view dosimetrics (BEVD) information to improve the computational efficiency and plan quality of inverse planning of aperture-modulated arc therapy (AMAT). Methods and Materials: In BEVD-guided inverse planning, the angular space spanned by a rotational arc is represented by a large number of fixed-gantry beams with angular spacing of ∼2.5 degrees. Each beam is assigned with an initial aperture shape determined by the beam's-eye-view (BEV) projection of the planning target volume (PTV) and an initial weight. Instead of setting the beam weights arbitrarily, which slows down the subsequent optimization process and may result in a suboptimal solution, a priori knowledge about the quality of the beam directions derived from a BEVD is adopted to initialize the weights. In the BEVD calculation, a higher score is assigned to directions that allow more dose to be delivered to the PTV without exceeding the dose tolerances of the organs at risk (OARs) and vice versa. Simulated annealing is then used to optimize the segment shapes and weights. The BEVD-guided inverse planning is demonstrated by using two clinical cases, and the results are compared with those of a conventional approach without BEVD guidance. Results: An a priori knowledge-guided inverse planning scheme for AMAT is established. The inclusion of BEVD guidance significantly improves the convergence behavior of AMAT inverse planning and results in much better OAR sparing as compared with the conventional approach. Conclusions: BEVD-guidance facilitates AMAT treatment planning and provides a comprehensive tool to maximally use the technical capacity of the new arc therapeutic modality.

Design of arc power supply for neutral beam injection system based on super capacitor energy storage

International Nuclear Information System (INIS)

Yang Puqiong; Xuan Weimin; Cao Jianyong; Li Qing; Liu Xiaolong

2015-01-01

The arc power supply is one of the most important equipment for neutral beam injection system. The stability of arc discharge and the quality of ion beam extraction were determined by its performance. For improving stability of the arc discharge, reducing the power network capacity and decreasing impulse on power network, the topology of the arc power supply applied the structure of DC/DC converter based on technology of super capacitor energy storage and switching power supply. Several IGBT power modules are operated in parallel, and it can improve the arc power supply's operating frequency and dynamic response. A filter circuit and a current fast transferring circuit were designed based on a detailed analysis on working process of the arc power sup- ply. According to the requirements and parameters of the arc power supply, and the current response of RL first order circuit, the minimum filter inductances were accurately calculated. Finally, using the model and Matlab, the performance of the arc power supply was simulated and verified, and it meets the design requirement. (authors)

Performance of the CEBAF Arc Beam Position Monitors

International Nuclear Information System (INIS)

A.S. Hofler; B.A. Bowling; C.S. Higgins; P.K. Kloeppel; G.A. Krafft; K.L. Mahoney

1993-01-01

The first three quarters of the first CEBAF arc have been instrumented with beam position monitors. Thirty-seven monitors (of 450) have been installed and their noise measured. Resolution of 100 mu-m was obtained at the lowest operating current of 1 mu-A. The update time of the system is 1 sec, limited by computer interfacing with a potential bandwidth of greater than 10 kHz

Shunting arc plasma source for pure carbon ion beam

Energy Technology Data Exchange (ETDEWEB)

Koguchi, H.; Sakakita, H.; Kiyama, S.; Shimada, T.; Sato, Y.; Hirano, Y. [Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan)

2012-02-15

A plasma source is developed using a coaxial shunting arc plasma gun to extract a pure carbon ion beam. The pure carbon ion beam is a new type of deposition system for diamond and other carbon materials. Our plasma device generates pure carbon plasma from solid-state carbon material without using a hydrocarbon gas such as methane gas, and the plasma does not contain any hydrogen. The ion saturation current of the discharge measured by a double probe is about 0.2 mA/mm{sup 2} at the peak of the pulse.

Shunting arc plasma source for pure carbon ion beam.

Science.gov (United States)

Koguchi, H; Sakakita, H; Kiyama, S; Shimada, T; Sato, Y; Hirano, Y

2012-02-01

A plasma source is developed using a coaxial shunting arc plasma gun to extract a pure carbon ion beam. The pure carbon ion beam is a new type of deposition system for diamond and other carbon materials. Our plasma device generates pure carbon plasma from solid-state carbon material without using a hydrocarbon gas such as methane gas, and the plasma does not contain any hydrogen. The ion saturation current of the discharge measured by a double probe is about 0.2 mA∕mm(2) at the peak of the pulse.

Beam trajectory acquisition system for the arcs of the Stanford Linear Collider

International Nuclear Information System (INIS)

Pellegrin, J.L.; Ross, M.C.; Scott, B.D.; Wilson, D.S.

1987-02-01

This report describes the beam position monitoring system of the collider arcs at the Stanford Linear Collider. This beam position monitoring system is different from others at SLAC in its large amount of hardware and its use of ungated, self-triggered electronics. All of the processing electronics are installed in the accelerator tunnel

Design of the extraction arc for the 2nd beam line of the free-electron laser FLASH

International Nuclear Information System (INIS)

Scholz, Matthias

2014-01-01

In this thesis, I deal with the design of the extraction arc for the second beam line of FLASH, an FEL (Free-Electron Laser) user facility at DESY Hamburg. Both beam lines will use the same linear accelerator and their separation will take place behind the last accelerating module. I present the constraints for the extraction arc given by the beam line layout of the existing machine, by the building environment of the new beam line and in particular, by coherent synchrotron radiation (CSR). The impact from CSR is presented, and I show how to mitigate these effects and what that means for the beam line design. The optimization of the extraction arc was done applying the downhill simplex algorithm which is presented, first in its basic form to explain the operation principle and then in a more advanced version as used in the applied program. I introduce in this thesis the final layout of the extraction arc including the following matching section. This layout fulfills all given constraints and can provide the required electron beam quality for FEL operation. In order to prove this, I present start-to-end simulations for different bunch charges and for two different wavelengths.

Quantitative analysis of beam delivery parameters and treatment process time for proton beam therapy

International Nuclear Information System (INIS)

Suzuki, Kazumichi; Gillin, Michael T.; Sahoo, Narayan; Zhu, X. Ronald; Lee, Andrew K.; Lippy, Denise

2011-01-01

Purpose: To evaluate patient census, equipment clinical availability, maximum daily treatment capacity, use factor for major beam delivery parameters, and treatment process time for actual treatments delivered by proton therapy systems. Methods: The authors have been recording all beam delivery parameters, including delivered dose, energy, range, spread-out Bragg peak widths, gantry angles, and couch angles for every treatment field in an electronic medical record system. We analyzed delivery system downtimes that had been recorded for every equipment failure and associated incidents. These data were used to evaluate the use factor of beam delivery parameters, the size of the patient census, and the equipment clinical availability of the facility. The duration of each treatment session from patient walk-in and to patient walk-out of the treatment room was measured for 82 patients with cancers at various sites. Results: The yearly average equipment clinical availability in the last 3 yrs (June 2007-August 2010) was 97%, which exceeded the target of 95%. Approximately 2200 patients had been treated as of August 2010. The major disease sites were genitourinary (49%), thoracic (25%), central nervous system (22%), and gastrointestinal (2%). Beams have been delivered in approximately 8300 treatment fields. The use factor for six beam delivery parameters was also evaluated. Analysis of the treatment process times indicated that approximately 80% of this time was spent for patient and equipment setup. The other 20% was spent waiting for beam delivery and beam on. The total treatment process time can be expressed by a quadratic polynomial of the number of fields per session. The maximum daily treatment capacity of our facility using the current treatment processes was estimated to be 133 ± 35 patients. Conclusions: This analysis shows that the facility has operated at a high performance level and has treated a large number of patients with a variety of diseases. The use

Dosimetric study of RapidArc plans with flattened beam (FB and flattening filter-free (FFF beam for localized prostate cancer based on physical indices

Directory of Open Access Journals (Sweden)

Birendra Kumar Rout

2014-12-01

Full Text Available Purpose: To identify the continual diversity between flattening photon beam (FB and Flattening Filter Free (FFF photon beams for localized prostate cancer; and to determine potential benefits and drawbacks of using unflattened beam for this type of treatment.Methods: Eight prostate cases including seminal vesicles selected for this study. The primary planning target volume (PTVP and boost planning target volume (PTVB were contoured. The total prescription dose was 78 Gy (56 Gy to PTVP and an additional 22 Gy to PTVB. For all cases, treatment plans using 6MV with FB and FFF beams with identical dose-volume constraints, arc angles and number of arcs were developed. The dose volume histograms for both techniques were compared for primary target volume and critical structures.Results: A low Sigma index (FFF: 1.65 + 0.361; FB: 1.725 + 0.39 indicating improved dose homogeneity in FFF beam. Conformity index (FFF: 0.994 + 0.01; FB: 0.993 + 0.01 is comparable for both techniques. Minimal difference of Organ at risk mean dose was observed. Normal tissue integral dose in FB plan resulted 1.5% lower than FFF plan. All the plans displayed significant increase (1.18 times for PTVP and 1.11 for PTBB in the average number of necessary MU with FFF beam.Conclusion: Diversity between FB and FFF beam plans were found. FFF beam accelerator has been utilized to develop clinically acceptable Rapid Arc treatment plans for prostate cancer with 6 MV.---------------------------------Cite this article as: Rout BK, Muralidhar KR, Ali M, Shekar MC, Kumar A. Dosimetric study of RapidArc plans with flattened beam (FB and flattening filter-free (FFF beam for localized prostate cancer based on physical indices. Int J Cancer Ther Oncol 2014; 2(4:02046.  DOI: 10.14319/ijcto.0204.6

Quality correction factors of composite IMRT beam deliveries: Theoretical considerations

International Nuclear Information System (INIS)

Bouchard, Hugo

2012-01-01

Purpose: In the scope of intensity modulated radiation therapy (IMRT) dosimetry using ionization chambers, quality correction factors of plan-class-specific reference (PCSR) fields are theoretically investigated. The symmetry of the problem is studied to provide recommendable criteria for composite beam deliveries where correction factors are minimal and also to establish a theoretical limit for PCSR delivery k Q factors. Methods: The concept of virtual symmetric collapsed (VSC) beam, being associated to a given modulated composite delivery, is defined in the scope of this investigation. Under symmetrical measurement conditions, any composite delivery has the property of having a k Q factor identical to its associated VSC beam. Using this concept of VSC, a fundamental property of IMRT k Q factors is demonstrated in the form of a theorem. The sensitivity to the conditions required by the theorem is thoroughly examined. Results: The theorem states that if a composite modulated beam delivery produces a uniform dose distribution in a volume V cyl which is symmetric with the cylindrical delivery and all beams fulfills two conditions in V cyl : (1) the dose modulation function is unchanged along the beam axis, and (2) the dose gradient in the beam direction is constant for a given lateral position; then its associated VSC beam produces no lateral dose gradient in V cyl , no matter what beam modulation or gantry angles are being used. The examination of the conditions required by the theorem lead to the following results. The effect of the depth-dose gradient not being perfectly constant with depth on the VSC beam lateral dose gradient is found negligible. The effect of the dose modulation function being degraded with depth on the VSC beam lateral dose gradient is found to be only related to scatter and beam hardening, as the theorem holds also for diverging beams. Conclusions: The use of the symmetry of the problem in the present paper leads to a valuable theorem showing

Design and Control of Small Neutral Beam Arc Chamber for Investigations of DIII-D Neutral Beam Failure During Helium Operation

Science.gov (United States)

Fremlin, Carl; Beckers, Jasper; Crowley, Brendan; Rauch, Joseph; Scoville, Jim

2017-10-01

The Neutral Beam system on the DIII-D tokamak consists of eight ion sources using the Common Long Pulse Source (CLPS) design. During helium operation, desired for research regarding the ITER pre-nuclear phase, it has been observed that the ion source arc chamber performance steadily deteriorates, eventually failing due to electrical breakdown of the insulation. A significant investment of manpower and time is required for repairs. To study the cause of failure a small analogue of the DIII-D neutral beam arc chamber has been constructed. This poster presents the design and analysis of the arc chamber including the PLC based operational control system for the experiment, analysis of the magnetic confinement and details of the diagnostic suite. Work supported in part by US DoE under the Science Undergraduate Laboratory Internship (SULI) program and under DE-FC02-04ER54698.

Flat panel detector-based cone beam computed tomography with a circle-plus-two-arcs data acquisition orbit: Preliminary phantom study

International Nuclear Information System (INIS)

Ning Ruola; Tang Xiangyang; Conover, David; Yu Rongfeng

2003-01-01

Cone beam computed tomography (CBCT) has been investigated in the past two decades due to its potential advantages over a fan beam CT. These advantages include (a) great improvement in data acquisition efficiency, spatial resolution, and spatial resolution uniformity, (b) substantially better utilization of x-ray photons generated by the x-ray tube compared to a fan beam CT, and (c) significant advancement in clinical three-dimensional (3D) CT applications. However, most studies of CBCT in the past are focused on cone beam data acquisition theories and reconstruction algorithms. The recent development of x-ray flat panel detectors (FPD) has made CBCT imaging feasible and practical. This paper reports a newly built flat panel detector-based CBCT prototype scanner and presents the results of the preliminary evaluation of the prototype through a phantom study. The prototype consisted of an x-ray tube, a flat panel detector, a GE 8800 CT gantry, a patient table and a computer system. The prototype was constructed by modifying a GE 8800 CT gantry such that both a single-circle cone beam acquisition orbit and a circle-plus-two-arcs orbit can be achieved. With a circle-plus-two-arcs orbit, a complete set of cone beam projection data can be obtained, consisting of a set of circle projections and a set of arc projections. Using the prototype scanner, the set of circle projections were acquired by rotating the x-ray tube and the FPD together on the gantry, and the set of arc projections were obtained by tilting the gantry while the x-ray tube and detector were at the 12 and 6 o'clock positions, respectively. A filtered backprojection exact cone beam reconstruction algorithm based on a circle-plus-two-arcs orbit was used for cone beam reconstruction from both the circle and arc projections. The system was first characterized in terms of the linearity and dynamic range of the detector. Then the uniformity, spatial resolution and low contrast resolution were assessed using

Specialty flat-top beam delivery fibers with controlled beam parameter product

Science.gov (United States)

Jollivet, C.; Farley, K.; Conroy, M.; Abramczyk, J.; Belke, S.; Becker, F.; Tankala, K.

2016-03-01

Beam delivery fibers have been used widely for transporting the optical beams from the laser to the subject of irradiation in a variety of markets including industrial, medical and defense applications. Standard beam delivery fibers range from 50 to 1500 μm core diameter and are used to guide CW or pulsed laser light, generated by solid state, fiber or diode lasers. Here, we introduce a novel fiber technology capable of simultaneously controlling the beam profile and the angular divergence of single-mode (SM) and multi-mode (MM) beams using a single-optical fiber. Results of beam transformation from a SM to a MM beam with flat-top intensity profile are presented in the case of a controlled BPP at 3.8 mm*mrad. The scaling capabilities of this flat-top fiber design to achieve a range of BPP values while ensuring a flat-top beam profile are discussed. In addition, we demonstrate, for the first time to the best of our knowledge, the homogenizer capabilities of this novel technology, able to transform random MM beams into uniform flat-top beam profiles with very limited impact on the beam brightness. This study is concluded with a discussion on the scalability of this fiber technology to fit from 50 up to 1500 μm core fibers and its potential for a broader range of applications.

Helical Tomotherapy Versus Single-Arc Intensity-Modulated Arc Therapy: A Collaborative Dosimetric Comparison Between Two Institutions

International Nuclear Information System (INIS)

Rong Yi; Tang, Grace; Welsh, James S.; Mohiuddin, Majid M.; Paliwal, Bhudatt; Yu, Cedric X.

2011-01-01

Purpose: Both helical tomotherapy (HT) and single-arc intensity-modulated arc therapy (IMAT) deliver radiation using rotational beams with multileaf collimators. We report a dual-institution study comparing dosimetric aspects of these two modalities. Methods and Materials: Eight patients each were selected from the University of Maryland (UMM) and the University of Wisconsin Cancer Center Riverview (UWR), for a total of 16 cases. Four cancer sites including brain, head and neck (HN), lung, and prostate were selected. Single-arc IMAT plans were generated at UMM using Varian RapidArc (RA), and HT plans were generated at UWR using Hi-Art II TomoTherapy. All 16 cases were planned based on the identical anatomic contours, prescriptions, and planning objectives. All plans were swapped for analysis at the same time after final approval. Dose indices for targets and critical organs were compared based on dose-volume histograms, the beam-on time, monitor units, and estimated leakage dose. After the disclosure of comparison results, replanning was done for both techniques to minimize diversity in optimization focus from different operators. Results: For the 16 cases compared, the average beam-on time was 1.4 minutes for RA and 4.8 minutes for HT plans. HT provided better target dose homogeneity (7.6% for RA and 4.2% for HT) with a lower maximum dose (110% for RA and 105% for HT). Dose conformation numbers were comparable, with RA being superior to HT (0.67 vs. 0.60). The doses to normal tissues using these two techniques were comparable, with HT showing lower doses for more critical structures. After planning comparison results were exchanged, both techniques demonstrated improvements in dose distributions or treatment delivery times. Conclusions: Both techniques created highly conformal plans that met or exceeded the planning goals. The delivery time and total monitor units were lower in RA than in HT plans, whereas HT provided higher target dose uniformity.

Analysis of the beam induced heat loads on the LHC arc beam screens during Run 2

CERN Document Server

Iadarola, Giovanni; Dijkstal, Philipp; Mether, Lotta; CERN. Geneva. ATS Department

2017-01-01

During Run 2 the Large Hadron Collider (LHC) has been routinely operated with 25 ns bunch spacing. In these conditions large heat loads have been measured on the beam screens of the superconducting magnets, together with other observations indicating that an electron cloud develops in the beam chambers. The analysis of these heat loads has revealed several interesting features allowing to pinpoint peculiar characteristics of the observed beam-induced heating. This document describes the main findings of this analysis including the evolution taking place during the run, the observed dependence on the beam conditions and the results from special tests and dedicated instrumentation. The differences observed in the behavior of the eight LHC arcs are also discussed.

Poster — Thur Eve — 33: The Influence of a Modeled Treatment Couch on Dose Distributions During IMRT and RapidArc Treatment Delivery

International Nuclear Information System (INIS)

Aldosary, Ghada; Nobah, Ahmad; Al-Zorkani, Faisal; Moftah, Belal; Devic, Slobodan

2014-01-01

Treatment couches have been known to perturb dose delivery in patients. This effect is most pronounced in techniques such as IMRT and RapidArc. Although modern treatment planning systems (TPS) include data for a “default” treatment couch, actual couches are not manufactured identically. Thus, variations in their Hounsfield Unit (HU) values may exist. This study demonstrates a practical and simple method of acquiring reliable HU data for any treatment couch. We also investigate the effects of both the default and modeled treatment couches on absorbed dose. Experimental verifications show that by neglecting to incorporate the treatment couch in the TPS, dose differences of up to 9.5% and 7.3% were present for 4 MV and 10 MV photon beams, respectively. Furthermore, a clinical study based on a cohort of 20 RapidArc and IMRT (brain, pelvis and abdominal) cases is performed. 2D dose distributions show that without the couch in the planning phase, differences ≤ 4.6% and 5.9% for RapidArc and IMRT cases are present for the same cases that the default couch was added to. Additionally, in comparison to the default couch, employing the modeled couch in the calculation process influences dose distributions by ≤ 2.7% and 8% for RapidArc and IMRT cases, respectively. This result was found to be site specific; where an accurate couch proves to be preferable for IMRT brain plans. As such, adding the couch during dose calculation decreases dose calculation errors, and a precisely modeled treatment couch offers higher dose delivery accuracy for brain treatment using IMRT

Poster — Thur Eve — 33: The Influence of a Modeled Treatment Couch on Dose Distributions During IMRT and RapidArc Treatment Delivery

Energy Technology Data Exchange (ETDEWEB)

Aldosary, Ghada [Medical Physics Unit, Montreal General Hospital, McGill University, Montreal, Quebec (Canada); Nobah, Ahmad; Al-Zorkani, Faisal; Moftah, Belal [Biomedical Physics Department, King Faisal Specialist Hospital and Research Center, Riyadh (Saudi Arabia); Devic, Slobodan [Department of Radiation Oncology, Jewish General Hospital, McGill University, Montreal, Quebec (Canada)

2014-08-15

Treatment couches have been known to perturb dose delivery in patients. This effect is most pronounced in techniques such as IMRT and RapidArc. Although modern treatment planning systems (TPS) include data for a “default” treatment couch, actual couches are not manufactured identically. Thus, variations in their Hounsfield Unit (HU) values may exist. This study demonstrates a practical and simple method of acquiring reliable HU data for any treatment couch. We also investigate the effects of both the default and modeled treatment couches on absorbed dose. Experimental verifications show that by neglecting to incorporate the treatment couch in the TPS, dose differences of up to 9.5% and 7.3% were present for 4 MV and 10 MV photon beams, respectively. Furthermore, a clinical study based on a cohort of 20 RapidArc and IMRT (brain, pelvis and abdominal) cases is performed. 2D dose distributions show that without the couch in the planning phase, differences ≤ 4.6% and 5.9% for RapidArc and IMRT cases are present for the same cases that the default couch was added to. Additionally, in comparison to the default couch, employing the modeled couch in the calculation process influences dose distributions by ≤ 2.7% and 8% for RapidArc and IMRT cases, respectively. This result was found to be site specific; where an accurate couch proves to be preferable for IMRT brain plans. As such, adding the couch during dose calculation decreases dose calculation errors, and a precisely modeled treatment couch offers higher dose delivery accuracy for brain treatment using IMRT.

Beam loss detection system in the arcs of the LHC

Science.gov (United States)

Arauzo, A.; Bovet, C.

2000-11-01

Over the whole circumference of the LHC, Beam Loss Monitors (BLM) will be needed for a continuous surveillance of fast and slow beam losses. In this paper, the location of the BLMs set outside the magnet cryostats in the arcs is proposed. In order to know the number of protons lost on the beam screen, the sensitivity of each BLM has been computed using the program GEANT 3.21, which generates the shower inside the cryostat. The material and the magnetic fields have been described thoroughly in 3-D and the simulation results show the best locations for 6 BLMs needed around each quadrupole. The number of minimum ionizing particles received for each lost proton serves to define local thresholds to dump the beam when the losses are menacing to quench a magnet.

Beam loss detection system in the arcs of the LHC

International Nuclear Information System (INIS)

Arauzo, A.; Bovet, C.

2000-01-01

Over the whole circumference of the LHC, Beam Loss Monitors (BLM) will be needed for a continuous surveillance of fast and slow beam losses. In this paper, the location of the BLMs set outside the magnet cryostats in the arcs is proposed. In order to know the number of protons lost on the beam screen, the sensitivity of each BLM has been computed using the program GEANT 3.21, which generates the shower inside the cryostat. The material and the magnetic fields have been described thoroughly in 3-D and the simulation results show the best locations for 6 BLMs needed around each quadrupole. The number of minimum ionizing particles received for each lost proton serves to define local thresholds to dump the beam when the losses are menacing to quench a magnet

Dosimetric evaluation of the interplay effect in respiratory-gated RapidArc radiation therapy

International Nuclear Information System (INIS)

Riley, Craig; Yang, Yong; Li, Tianfang; Zhang, Yongqian; Heron, Dwight E.; Huq, M. Saiful

2014-01-01

Purpose: Volumetric modulated arc therapy (VMAT) with gating capability has had increasing adoption in many clinics in the United States. In this new technique, dose rate, gantry rotation speed, and the leaf motion speed of multileaf collimators (MLCs) are modulated dynamically during gated beam delivery to achieve highly conformal dose coverage of the target and normal tissue sparing. Compared with the traditional gated intensity-modulated radiation therapy technique, this complicated beam delivery technique may result in larger dose errors due to the intrafraction tumor motion. The purpose of this work is to evaluate the dosimetric influence of the interplay effect for the respiration-gated VMAT technique (RapidArc, Varian Medical Systems, Palo Alto, CA). Our work consisted of two parts: (1) Investigate the interplay effect for different target residual errors during gated RapidArc delivery using a one-dimensional moving phantom capable of producing stable sinusoidal movement; (2) Evaluate the dosimetric influence in ten clinical patients’ treatment plans using a moving phantom driven with a patient-specific respiratory curve. Methods: For the first part of this study, four plans were created with a spherical target for varying residual motion of 0.25, 0.5, 0.75, and 1.0 cm. Appropriate gating windows were applied for each. The dosimetric effect was evaluated using EDR2 film by comparing the gated delivery with static delivery. For the second part of the project, ten gated lung stereotactic body radiotherapy cases were selected and reoptimized to be delivered by the gated RapidArc technique. These plans were delivered to a phantom, and again the gated treatments were compared to static deliveries by the same methods. Results: For regular sinusoidal motion, the dose delivered to the target was not substantially affected by the gating windows when evaluated with the gamma statistics, suggesting the interplay effect has a small role in respiratory-gated RapidArc

Dosimetric evaluation of the interplay effect in respiratory-gated RapidArc radiation therapy.

Science.gov (United States)

Riley, Craig; Yang, Yong; Li, Tianfang; Zhang, Yongqian; Heron, Dwight E; Huq, M Saiful

2014-01-01

Volumetric modulated arc therapy (VMAT) with gating capability has had increasing adoption in many clinics in the United States. In this new technique, dose rate, gantry rotation speed, and the leaf motion speed of multileaf collimators (MLCs) are modulated dynamically during gated beam delivery to achieve highly conformal dose coverage of the target and normal tissue sparing. Compared with the traditional gated intensity-modulated radiation therapy technique, this complicated beam delivery technique may result in larger dose errors due to the intrafraction tumor motion. The purpose of this work is to evaluate the dosimetric influence of the interplay effect for the respiration-gated VMAT technique (RapidArc, Varian Medical Systems, Palo Alto, CA). Our work consisted of two parts: (1) Investigate the interplay effect for different target residual errors during gated RapidArc delivery using a one-dimensional moving phantom capable of producing stable sinusoidal movement; (2) Evaluate the dosimetric influence in ten clinical patients' treatment plans using a moving phantom driven with a patient-specific respiratory curve. For the first part of this study, four plans were created with a spherical target for varying residual motion of 0.25, 0.5, 0.75, and 1.0 cm. Appropriate gating windows were applied for each. The dosimetric effect was evaluated using EDR2 film by comparing the gated delivery with static delivery. For the second part of the project, ten gated lung stereotactic body radiotherapy cases were selected and reoptimized to be delivered by the gated RapidArc technique. These plans were delivered to a phantom, and again the gated treatments were compared to static deliveries by the same methods. For regular sinusoidal motion, the dose delivered to the target was not substantially affected by the gating windows when evaluated with the gamma statistics, suggesting the interplay effect has a small role in respiratory-gated RapidArc therapy. Varied results were

Sweeping-window arc therapy: an implementation of rotational IMRT with automatic beam-weight calculation

International Nuclear Information System (INIS)

Cameron, C

2005-01-01

Sweeping-window arc therapy (SWAT) is a variation of intensity-modulated radiation therapy (IMRT) with direct aperture optimization (DAO) that is initialized with a leaf sequence of sweeping windows that move back and forth periodically across the target as the gantry rotates. This initial sequence induces modulation in the dose and is assumed to be near enough to a minimum to allow successful optimization, done with simulated annealing, without requiring excessive leaf speeds. Optimal beam weights are calculated analytically, with easy extension to allow for variable beam weights. In this paper SWAT is tested on a phantom model and clinical prostate case. For the phantom, constant and variable beam weights are used. Although further work (in particular, improving the dose model) is required, the results show SWAT to be a feasible approach to generating deliverable dynamic arc treatments that are optimized

Sweeping-window arc therapy: an implementation of rotational IMRT with automatic beam-weight calculation

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Cameron, C [Division of Radiation Physics, Department of Radiation Oncology, Stanford Cancer Center, 875 Blake Wilbur Drive, Rm G-233, Stanford, CA 94305-5847 (United States)

2005-09-21

Sweeping-window arc therapy (SWAT) is a variation of intensity-modulated radiation therapy (IMRT) with direct aperture optimization (DAO) that is initialized with a leaf sequence of sweeping windows that move back and forth periodically across the target as the gantry rotates. This initial sequence induces modulation in the dose and is assumed to be near enough to a minimum to allow successful optimization, done with simulated annealing, without requiring excessive leaf speeds. Optimal beam weights are calculated analytically, with easy extension to allow for variable beam weights. In this paper SWAT is tested on a phantom model and clinical prostate case. For the phantom, constant and variable beam weights are used. Although further work (in particular, improving the dose model) is required, the results show SWAT to be a feasible approach to generating deliverable dynamic arc treatments that are optimized.

Volumetric modulated arc therapy with flattening filter free beams for isolated abdominal/pelvic lymph nodes: report of dosimetric and early clinical results in oligometastatic patients

Directory of Open Access Journals (Sweden)

Alongi Filippo

2012-12-01

Full Text Available Abstract Background SBRT is a safe and efficient strategy to locally control multiple metastatic sites. While research in the physics domain for Flattening Filter Free Beams (FFF beams is increasing, there are few clinical data of FFF beams in clinical practice. Here we reported dosimentric and early clinical data of SBRT and FFF delivery in isolated lymph node oligometastatic patients. Methods Between October 2010 and March 2012, 34 patients were treated with SBRT for oligometastatic lymph node metastasis on a Varian TrueBeamTM treatment machine using Volumetric Modulated Arc Therapy (RapidArc. We retrospectively evaluated a total of 25 patients for isolated lymph node metastases in abdomen and/or pelvis treated with SBRT and FFF (28 treatments. Acute toxicity was recorded. Local control evaluation was scored by means of CT scan and/or PET scan. Results All dosimetric results are in line with what published for the same type of stereotactic abdominal lymph node metastases treatments and fractionation, using RapidArc. All 25 FFF SBRT patients completed the treatment. Acute gastrointestinal toxicity was minimal: one patient showed Grade 1 gastrointestinal toxicity. Three other patients presented Grade 2 toxicity. No Grade 3 or higher was recorded. All toxicities were recovered within one week. The preliminary clinical results at the median follow up of 195 days are: complete response in 12 cases, partial response in 11, stable disease in 5, with an overall response rate of 82%; no local progression was recorded. Conclusions Data of dosimetrical findings and acute toxicity are excellent for patients treated with SBRT with VMAT using FFF beams. Preliminary clinical results showed a high rate of local control in irradiated lesion. Further data and longer follow up are needed to assess late toxicity and definitive clinical outcomes.

Real-time 3D internal marker tracking during arc radiotherapy by the use of combined MV-kV imaging.

Science.gov (United States)

Liu, W; Wiersma, R D; Mao, W; Luxton, G; Xing, L

2008-12-21

To minimize the adverse dosimetric effect caused by tumor motion, it is desirable to have real-time knowledge of the tumor position throughout the beam delivery process. A promising technique to realize the real-time image guided scheme in external beam radiation therapy is through the combined use of MV and onboard kV beam imaging. The success of this MV-kV triangulation approach for fixed-gantry radiation therapy has been demonstrated. With the increasing acceptance of modern arc radiotherapy in the clinics, a timely and clinically important question is whether the image guidance strategy can be extended to arc therapy to provide the urgently needed real-time tumor motion information. While conceptually feasible, there are a number of theoretical and practical issues specific to the arc delivery that need to be resolved before clinical implementation. The purpose of this work is to establish a robust procedure of system calibration for combined MV and kV imaging for internal marker tracking during arc delivery and to demonstrate the feasibility and accuracy of the technique. A commercially available LINAC equipped with an onboard kV imager and electronic portal imaging device (EPID) was used for the study. A custom built phantom with multiple ball bearings was used to calibrate the stereoscopic MV-kV imaging system to provide the transformation parameters from imaging pixels to 3D world coordinates. The accuracy of the fiducial tracking system was examined using a 4D motion phantom capable of moving in accordance with a pre-programmed trajectory. Overall, spatial accuracy of MV-kV fiducial tracking during the arc delivery process for normal adult breathing amplitude and period was found to be better than 1 mm. For fast motion, the results depended on the imaging frame rates. The RMS error ranged from approximately 0.5 mm for the normal adult breathing pattern to approximately 1.5 mm for more extreme cases with a low imaging frame rate of 3.4 Hz. In general

Real-time 3D internal marker tracking during arc radiotherapy by the use of combined MV-kV imaging

International Nuclear Information System (INIS)

Liu, W; Wiersma, R D; Mao, W; Luxton, G; Xing, L

2008-01-01

To minimize the adverse dosimetric effect caused by tumor motion, it is desirable to have real-time knowledge of the tumor position throughout the beam delivery process. A promising technique to realize the real-time image guided scheme in external beam radiation therapy is through the combined use of MV and onboard kV beam imaging. The success of this MV-kV triangulation approach for fixed-gantry radiation therapy has been demonstrated. With the increasing acceptance of modern arc radiotherapy in the clinics, a timely and clinically important question is whether the image guidance strategy can be extended to arc therapy to provide the urgently needed real-time tumor motion information. While conceptually feasible, there are a number of theoretical and practical issues specific to the arc delivery that need to be resolved before clinical implementation. The purpose of this work is to establish a robust procedure of system calibration for combined MV and kV imaging for internal marker tracking during arc delivery and to demonstrate the feasibility and accuracy of the technique. A commercially available LINAC equipped with an onboard kV imager and electronic portal imaging device (EPID) was used for the study. A custom built phantom with multiple ball bearings was used to calibrate the stereoscopic MV-kV imaging system to provide the transformation parameters from imaging pixels to 3D world coordinates. The accuracy of the fiducial tracking system was examined using a 4D motion phantom capable of moving in accordance with a pre-programmed trajectory. Overall, spatial accuracy of MV-kV fiducial tracking during the arc delivery process for normal adult breathing amplitude and period was found to be better than 1 mm. For fast motion, the results depended on the imaging frame rates. The RMS error ranged from ∼0.5 mm for the normal adult breathing pattern to ∼1.5 mm for more extreme cases with a low imaging frame rate of 3.4 Hz. In general, highly accurate real

The GLAaS algorithm for portal dosimetry and quality assurance of RapidArc, an intensity modulated rotational therapy

International Nuclear Information System (INIS)

Nicolini, Giorgia; Vanetti, Eugenio; Clivio, Alessandro; Fogliata, Antonella; Korreman, Stine; Bocanek, Jiri; Cozzi, Luca

2008-01-01

To expand and test the dosimetric procedure, known as GLAaS, for amorphous silicon detectors to the RapidArc intensity modulated arc delivery with Varian infrastructures and to test the RapidArc dosimetric reliability between calculation and delivery. The GLAaS algorithm was applied and tested on a set of RapidArc fields at both low (6 MV) and high (18 MV) beam energies with a PV-aS1000 detector. Pilot tests for short arcs were performed on a 6 MV beam associated to a PV-aS500. RapidArc is a novel planning and delivery method in the category of intensity modulated arc therapies aiming to deliver highly modulated plans with variable MLC shapes, dose rate and gantry speed during rotation. Tests were repeated for entire (360 degrees) gantry rotations on composite dose plans and for short partial arcs (of ~6 or 12 degrees) to assess GLAaS and RapidArc mutual relationships on global and fine delivery scales. The gamma index concept of Low and the Modulation Index concept of Webb were applied to compare quantitatively TPS dose matrices and dose converted PV images. The Gamma Agreement Index computed for a Distance to Agreement of 3 mm and a Dose Difference (ΔD) of 3% was, as mean ± 1 SD, 96.7 ± 1.2% at 6 MV and 94.9 ± 1.3% at 18 MV, over the field area. These findings deteriorated slightly is ΔD was reduced to 2% (93.4 ± 3.2% and 90.1 ± 3.1%, respectively) and improved with ΔD = 4% (98.3 ± 0.8% and 97.3 ± 0.9%, respectively). For all tests a grid of 1 mm and the AAA photon dose calculation algorithm were applied. The spatial resolution of the PV-aS1000 is 0.392 mm/pxl. The Modulation Index for calculations resulted 17.0 ± 3.2 at 6 MV and 15.3 ± 2.7 at 18 MV while the corresponding data for measurements were: 18.5 ± 3.7 and 17.5 ± 3.7. Partial arcs findings were (for ΔD = 3%): GAI = 96.7 ± 0.9% for 6° rotations and 98.0 ± 1.1% for 12° rotations. The GLAaS method can be considered as a valid Quality Assurance tool for the verification of RapidArc fields

Volumetric modulated arc therapy: IMRT in a single gantry arc

International Nuclear Information System (INIS)

Otto, Karl

2008-01-01

In this work a novel plan optimization platform is presented where treatment is delivered efficiently and accurately in a single dynamically modulated arc. Improvements in patient care achieved through image-guided positioning and plan adaptation have resulted in an increase in overall treatment times. Intensity-modulated radiation therapy (IMRT) has also increased treatment time by requiring a larger number of beam directions, increased monitor units (MU), and, in the case of tomotherapy, a slice-by-slice delivery. In order to maintain a similar level of patient throughput it will be necessary to increase the efficiency of treatment delivery. The solution proposed here is a novel aperture-based algorithm for treatment plan optimization where dose is delivered during a single gantry arc of up to 360 deg. The technique is similar to tomotherapy in that a full 360 deg. of beam directions are available for optimization but is fundamentally different in that the entire dose volume is delivered in a single source rotation. The new technique is referred to as volumetric modulated arc therapy (VMAT). Multileaf collimator (MLC) leaf motion and number of MU per degree of gantry rotation is restricted during the optimization so that gantry rotation speed, leaf translation speed, and dose rate maxima do not excessively limit the delivery efficiency. During planning, investigators model continuous gantry motion by a coarse sampling of static gantry positions and fluence maps or MLC aperture shapes. The technique presented here is unique in that gantry and MLC position sampling is progressively increased throughout the optimization. Using the full gantry range will theoretically provide increased flexibility in generating highly conformal treatment plans. In practice, the additional flexibility is somewhat negated by the additional constraints placed on the amount of MLC leaf motion between gantry samples. A series of studies are performed that characterize the relationship

Beam delivery system with a non-digitized diffractive beam splitter for laser-drilling of silicon

Science.gov (United States)

Amako, J.; Fujii, E.

2016-02-01

We report a beam-delivery system consisting of a non-digitized diffractive beam splitter and a Fourier transform lens. The system is applied to the deep-drilling of silicon using a nanosecond pulse laser in the manufacture of inkjet printer heads. In this process, a circularly polarized pulse beam is divided into an array of uniform beams, which are then delivered precisely to the process points. To meet these requirements, the splitter was designed to be polarization-independent with an efficiency>95%. The optical elements were assembled so as to allow the fine tuning of the effective overall focal length by adjusting the wavefront curvature of the beam. Using the system, a beam alignment accuracy ofbeam array and the throughput was substantially improved (10,000 points on a silicon wafer drilled in ~1 min). This beam-delivery scheme works for a variety of laser applications that require parallel processing.

The dosimetric impact of inversely optimized arc radiotherapy plan modulation for real-time dynamic MLC tracking delivery

International Nuclear Information System (INIS)

Falk, Marianne; Larsson, Tobias; Keall, Paul; Chul Cho, Byung; Aznar, Marianne; Korreman, Stine; Poulsen, Per; Munck af Rosenschoeld, Per

2012-01-01

Purpose: Real-time dynamic multileaf collimator (MLC) tracking for management of intrafraction tumor motion can be challenging for highly modulated beams, as the leaves need to travel far to adjust for target motion perpendicular to the leaf travel direction. The plan modulation can be reduced by using a leaf position constraint (LPC) that reduces the difference in the position of adjacent MLC leaves in the plan. The purpose of this study was to investigate the impact of the LPC on the quality of inversely optimized arc radiotherapy plans and the effect of the MLC motion pattern on the dosimetric accuracy of MLC tracking delivery. Specifically, the possibility of predicting the accuracy of MLC tracking delivery based on the plan modulation was investigated. Methods: Inversely optimized arc radiotherapy plans were created on CT-data of three lung cancer patients. For each case, five plans with a single 358 deg. arc were generated with LPC priorities of 0 (no LPC), 0.25, 0.5, 0.75, and 1 (highest possible LPC), respectively. All the plans had a prescribed dose of 2 Gy x 30, used 6 MV, a maximum dose rate of 600 MU/min and a collimator angle of 45 deg. or 315 deg. To quantify the plan modulation, an average adjacent leaf distance (ALD) was calculated by averaging the mean adjacent leaf distance for each control point. The linear relationship between the plan quality [i.e., the calculated dose distributions and the number of monitor units (MU)] and the LPC was investigated, and the linear regression coefficient as well as a two tailed confidence level of 95% was used in the evaluation. The effect of the plan modulation on the performance of MLC tracking was tested by delivering the plans to a cylindrical diode array phantom moving with sinusoidal motion in the superior-inferior direction with a peak-to-peak displacement of 2 cm and a cycle time of 6 s. The delivery was adjusted to the target motion using MLC tracking, guided in real-time by an infrared optical system

An optimal algorithm for configuring delivery options of a one-dimensional intensity-modulated beam

International Nuclear Information System (INIS)

Luan Shuang; Chen, Danny Z; Zhang, Li; Wu Xiaodong; Yu, Cedric X

2003-01-01

The problem of generating delivery options for one-dimensional intensity-modulated beams (1D IMBs) arises in intensity-modulated radiation therapy. In this paper, we present an algorithm with the optimal running time, based on the 'rightmost-preference' method, for generating all distinct delivery options for an arbitrary 1D IMB. The previously best known method for generating delivery options for a 1D IMB with N left leaf positions and N right leaf positions is a 'brute-force' solution, which first generates all N! possible combinations of the left and right leaf positions and then removes combinations that are not physically allowed delivery options. Compared with the brute-force method, our algorithm has several advantages: (1) our algorithm runs in an optimal time that is linearly proportional to the total number of distinct delivery options that it actually produces. Note that for a 1D IMB with multiple peaks, the total number of distinct delivery options in general tends to be considerably smaller than the worst case N!. (2) Our algorithm can be adapted to generating delivery options subject to additional constraints such as the 'minimum leaf separation' constraint. (3) Our algorithm can also be used to generate random subsets of delivery options; this feature is especially useful when the 1D IMBs in question have too many delivery options for a computer to store and process. The key idea of our method is that we impose an order on how left leaf positions should be paired with right leaf positions. Experiments indicated that our rightmost-preference algorithm runs dramatically faster than the brute-force algorithm. This implies that our algorithm can handle 1D IMBs whose sizes are substantially larger than those handled by the brute-force method. Applications of our algorithm in therapeutic techniques such as intensity-modulated arc therapy and 2D modulations are also discussed

SU-E-T-508: End to End Testing of a Prototype Eclipse Module for Planning Modulated Arc Therapy On the Siemens Platform

International Nuclear Information System (INIS)

Huang, L; Sarkar, V; Spiessens, S; Rassiah-Szegedi, P; Huang, Y; Salter, B; Zhao, H; Szegedi, M

2014-01-01

Purpose: The latest clinical implementation of the Siemens Artiste linac allows for delivery of modulated arcs (mARC) using full-field flattening filter free (FFF) photon beams. The maximum doserate of 2000 MU/min is well suited for high dose treatments such as SBRT. We tested and report on the performance of a prototype Eclipse TPS module supporting mARC capability on the Artiste platform. Method: our spine SBRT patients originally treated with 12/13 field static-gantry IMRT (SGIMRT) were chosen for this study. These plans were designed to satisfy RTOG0631 guidelines with a prescription of 16Gy in a single fraction. The cases were re-planned as mARC plans in the prototype Eclipse module using the 7MV FFF beam and required to satisfy RTOG0631 requirements. All plans were transferred from Eclipse, delivered on a Siemens Artiste linac and dose-validated using the Delta4 system. Results: All treatment plans were straightforwardly developed, in timely fashion, without challenge or inefficiency using the prototype module. Due to the limited number of segments in a single arc, mARC plans required 2-3 full arcs to yield plan quality comparable to SGIMRT plans containing over 250 total segments. The average (3%/3mm) gamma pass-rate for all arcs was 98.5±1.1%, thus demonstrating both excellent dose prediction by the AAA dose algorithm and excellent delivery fidelity. Mean delivery times for the mARC plans(10.5±1.7min) were 50-70% lower than the SGIMRT plans(26±2min), with both delivered at 2000 MU/min. Conclusion: A prototype Eclipse module capable of planning for Burst Mode modulated arc delivery on the Artiste platform has been tested and found to perform efficiently and accurately for treatment plan development and delivered-dose prediction. Further investigation of more treatment sites is being carried out and data will be presented

Comparative estimation of the properties of heat resisting nickel alloy welded joints made by electron-beam and arc welding

International Nuclear Information System (INIS)

Morochko, V.P.; Sorokin, L.I.; Yakushin, B.F.; Moryakov, V.F.

1977-01-01

As compared to argon arc welding of refractory nickel alloys at 15 m/hour rate, electron beam welding decreases energy consumption per unit length (from 4300 to 2070 cal/cm), the weld area (from 108 to 24 mm 2 ), and the length of the thermal effect zone (from 0.9-1.8 to 0.4-0.8 mm). Electron beam welding also provides for better resistance to hot cracking in the weld metal and in the near-weld zone, as compared to automatic argon arc welding and manual welding with addition of the basic metal. However, this advantage is observed only at welding rates less than 45 m/hour. Electron beam welded joints of refractory nickel alloys with intermetallide reinforcement have higher strength, plasticity and impact strength, and lower scattering of these properties than arc welded joints

Dose error analysis for a scanned proton beam delivery system

International Nuclear Information System (INIS)

Coutrakon, G; Wang, N; Miller, D W; Yang, Y

2010-01-01

All particle beam scanning systems are subject to dose delivery errors due to errors in position, energy and intensity of the delivered beam. In addition, finite scan speeds, beam spill non-uniformities, and delays in detector, detector electronics and magnet responses will all contribute errors in delivery. In this paper, we present dose errors for an 8 x 10 x 8 cm 3 target of uniform water equivalent density with 8 cm spread out Bragg peak and a prescribed dose of 2 Gy. Lower doses are also analyzed and presented later in the paper. Beam energy errors and errors due to limitations of scanning system hardware have been included in the analysis. By using Gaussian shaped pencil beams derived from measurements in the research room of the James M Slater Proton Treatment and Research Center at Loma Linda, CA and executing treatment simulations multiple times, statistical dose errors have been calculated in each 2.5 mm cubic voxel in the target. These errors were calculated by delivering multiple treatments to the same volume and calculating the rms variation in delivered dose at each voxel in the target. The variations in dose were the result of random beam delivery errors such as proton energy, spot position and intensity fluctuations. The results show that with reasonable assumptions of random beam delivery errors, the spot scanning technique yielded an rms dose error in each voxel less than 2% or 3% of the 2 Gy prescribed dose. These calculated errors are within acceptable clinical limits for radiation therapy.

Rapid arc in cancer treatment - a therapeutic perspective

International Nuclear Information System (INIS)

Rao, Suresh

2013-01-01

Recently, volumetric-modulated arc therapy (VMAT) has demonstrated the ability to deliver radiation dose precisely and accurately with a shorter delivery time compared to conventional intensity-modulated fixed-field treatment (IMRT). We applied the hypothesis of VMAT technique at our hospital to determine the superior dose coverage for planning target volume (PTV) with adequate sparing of organs-at-risk (OARs). The delivery time and monitor units (MUs) is reduced in comparison with conventional fixed-field IMRT. Rapid Arc (RA) plans had a pre-treatment quality assurance and results were summarised in terms of the Gamma Agreement Index (GAI) scoring criteria of 3% and 3 mm thresholds. A total of 771 patients were treated between July 2011 and August 2013 of which head and neck cancer were 385, prostate cancer 53, brain tumours 112, cervical and endometrial cancer 77, breast cancer 38, rectal and bladder cancer 56, special technique using SBRT 45 (Liver and Lung) and Cranio-spinal irradiation 5 patients using RA single (177 control points) and double arcs (354 control points). The Average treatment time was 4.8 ±0.2 minutes (220 seconds of beam-on). The number of MU per fraction of 2.0 Gy was 522.5 ± 133.62. VMAT can be a valuable clinical tool that can deliver the prescribed dose efficiently in 1.5-3 minutes (single or double arcs) with high target homogeneity and adequate sparing of organs at risk. It would allow to reduce patient lying time on couch and over all beam on time from 4 hours to one hour. The toxicity (Tracheal fistula) observed in two patients of Carcinoma Lung receiving SRT high lights the need for peer review. (author)

Increased power delivery from the DIII-D neutral beam injection system

International Nuclear Information System (INIS)

Colleraine, A.P.; Callis, R.W.; Hong, R.M.; Kellman, D.H.; Kim, J.; Langhorn, A.R.; Lee, R.; Phillips, J.C.; Wight, J.J.

1989-12-01

The neutral beam system installed on the DIII-D tokamak employs eight 80 kV Long Pulse Sources (LPS) mounted on four beamlines and was originally designed to deliver a nominal 12 MW of H degree power to a plasma for pulses of up to 5 sec duration. Lawrence Berkeley Laboratory designed the LPS for the US Fusion Program to fill the requirements of both the DIII-D and the TFTR machines. Essentially all source components are of a common design; the DIII-D version is therefore conservative in its rated parameters. Recently a neutron shield has been constructed around the torus hall allowing D degree injection to become routine. Because deuterium beams have a better neutralization efficiency, the nominal power delivery per source has been measured to be approximately 2 MW (for a total of 16 MW) without any modifications. However, by reoptimizing the voltage gradients in the source, the perveance can be increased without degrading the optics. A change of gradient grid voltage from 0.83 V accel to 0.79 V accel raises the perveance from 2.5 to 3.0 μPerv with a corresponding gain in beam power of about 20%. The arc power required also must be increased to the range of 100 to 120 kW but this is well within the design limits of the LPS. Further studies of our systems are now underway to assess the possibilities of raising V accel above 80 kV. An additional gain in power is possible by this technique. 6 refs., 6 figs

Beam-optics study of the gantry beam delivery system for light-ion cancer therapy

International Nuclear Information System (INIS)

Pavlovic, M.

1995-12-01

Ion optics considerations on the granty-like beam delivery system for light-ion cancer therapy are presented. A low-angle active beam scanning in two directions is included in the preliminary gantry design. The optical properties of several gantry modifications are discussed. (orig.)

Verification of Dosimetric Commissioning Accuracy of Intensity Modulated Radiation Therapy and Volumetric Modulated Arc Therapy Delivery using Task Group-119 Guidelines.

Science.gov (United States)

Kaviarasu, Karunakaran; Nambi Raj, N Arunai; Hamid, Misba; Giri Babu, A Ananda; Sreenivas, Lingampally; Murthy, Kammari Krishna

2017-01-01

The purpose of this study is to verify the accuracy of the commissioning of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) based on the recommendation of the American Association of Physicists in Medicine Task Group 119 (TG-119). TG-119 proposes a set of clinical test cases to verify the accuracy of IMRT planning and delivery system. For these test cases, we generated two sets of treatment plans, the first plan using 7-9 IMRT fields and a second plan utilizing two-arc VMAT technique for both 6 MV and 15 MV photon beams. The template plans of TG-119 were optimized and calculated by Varian Eclipse Treatment Planning System (version 13.5). Dose prescription and planning objectives were set according to the TG-119 goals. The point dose (mean dose to the contoured chamber volume) at the specified positions/locations was measured using compact (CC-13) ion chamber. The composite planar dose was measured with IMatriXX Evaluation 2D array with OmniPro IMRT Software (version 1.7b). The per-field relative gamma was measured using electronic portal imaging device in a way similar to the routine pretreatment patient-specific quality assurance. Our planning results are compared with the TG-119 data. Point dose and fluence comparison data where within the acceptable confident limit. From the obtained data in this study, we conclude that the commissioning of IMRT and VMAT delivery were found within the limits of TG-119.

SU-E-T-151: Breathing Synchronized Delivery (BSD) Planning for RapicArc Treatment

International Nuclear Information System (INIS)

Lu, W; Chen, M; Jiang, S

2015-01-01

Purpose: To propose a workflow for breathing synchronized delivery (BSD) planning for RapicArc treatment. Methods: The workflow includes three stages: screening/simulation, planning, and delivery. In the screening/simulation stage, a 4D CT with the corresponding breathing pattern is acquired for each of the selected patients, who are able to follow their own breathing pattern. In the planning stage, one breathing phase is chosen as the reference, and contours are delineated on the reference image. Deformation maps to other phases are performed along with contour propagation. Based on the control points of the initial 3D plan for the reference phase and the respiration trace, the correlation with respiration phases, the leaf sequence and gantry angles is determined. The beamlet matrices are calculated with the corresponding breathing phase and deformed to the reference phase. Using the 4D dose evaluation tool and the original 3D plan DVHs criteria, the leaf sequence is further optimized to meet the planning objectives and the machine constraints. In the delivery stage, the patients are instructed to follow the programmed breathing patterns of their own, and all other parts are the same as the conventional Rapid-Arc delivery. Results: Our plan analysis is based on comparison of the 3D plan with a static target (SD), 3D plan with motion delivery (MD), and the BSD plan. Cyclic motion of range 0 cm to 3 cm was simulated for phantoms and lung CT. The gain of the BSD plan over MD is significant and concordant for both simulation and lung 4DCT, indicating the benefits of 4D planning. Conclusion: Our study shows that the BSD plan can approach the SD plan quality. However, such BSD scheme relies on the patient being able to follow the same breathing curve that is used in the planning stage during radiation delivery. Funded by Varian Medical Systems

MO-FG-CAMPUS-TeP2-05: Optimizing Stereotactic Radiosurgery Treatment of Multiple Brain Metastasis Lesions with Individualized Rotational Arc Trajectories

International Nuclear Information System (INIS)

Dong, P; Xing, L; Ma, L

2016-01-01

Purpose: Radiosurgery of multiple (n>4) brain metastasis lesions requires 3–4 noncoplanar VMAT arcs with excessively high monitor units and long delivery time. We investigated whether an improved optimization technique would decrease the needed arc numbers and increase the delivery efficiency, while improving or maintaining the plan quality. Methods: The proposed 4pi arc space optimization algorithm consists of two steps: automatic couch angle selection followed by aperture generation for each arc with optimized control points distribution. We use a greedy algorithm to select the couch angles. Starting from a single coplanar arc plan we search through the candidate noncoplanar arcs to pick a single noncoplanar arc that will bring the best plan quality when added into the existing treatment plan. Each time, only one additional noncoplanar arc is considered making the calculation time tractable. This process repeats itself until desired number of arc is reached. The technique is first evaluated in coplanar arc delivery scheme with testing cases and then applied to noncoplanar treatments of a case with 12 brain metastasis lesions. Results: Clinically acceptable plans are created within minutes. For the coplanar testing cases the algorithm yields singlearc plans with better dose distributions than that of two-arc VMAT, simultaneously with a 12–17% reduction in the delivery time and a 14–21% reduction in MUs. For the treatment of 12 brain mets while Paddick conformity indexes of the two plans were comparable the SCG-optimization with 2 arcs (1 noncoplanar and 1 coplanar) significantly improved the conventional VMAT with 3 arcs (2 noncoplanar and 1 coplanar). Specifically V16 V10 and V5 of the brain were reduced by 11%, 11% and 12% respectively. The beam delivery time was shortened by approximately 30%. Conclusion: The proposed 4pi arc space optimization technique promises to significantly reduce the brain toxicity while greatly improving the treatment efficiency.

MO-FG-CAMPUS-TeP2-05: Optimizing Stereotactic Radiosurgery Treatment of Multiple Brain Metastasis Lesions with Individualized Rotational Arc Trajectories

Energy Technology Data Exchange (ETDEWEB)

Dong, P; Xing, L [Stanford University School of Medicine, Stanford, CA (United States); Ma, L [UCSF Comprehensive Cancer Center, San Francisco, CA (United States)

2016-06-15

Purpose: Radiosurgery of multiple (n>4) brain metastasis lesions requires 3–4 noncoplanar VMAT arcs with excessively high monitor units and long delivery time. We investigated whether an improved optimization technique would decrease the needed arc numbers and increase the delivery efficiency, while improving or maintaining the plan quality. Methods: The proposed 4pi arc space optimization algorithm consists of two steps: automatic couch angle selection followed by aperture generation for each arc with optimized control points distribution. We use a greedy algorithm to select the couch angles. Starting from a single coplanar arc plan we search through the candidate noncoplanar arcs to pick a single noncoplanar arc that will bring the best plan quality when added into the existing treatment plan. Each time, only one additional noncoplanar arc is considered making the calculation time tractable. This process repeats itself until desired number of arc is reached. The technique is first evaluated in coplanar arc delivery scheme with testing cases and then applied to noncoplanar treatments of a case with 12 brain metastasis lesions. Results: Clinically acceptable plans are created within minutes. For the coplanar testing cases the algorithm yields singlearc plans with better dose distributions than that of two-arc VMAT, simultaneously with a 12–17% reduction in the delivery time and a 14–21% reduction in MUs. For the treatment of 12 brain mets while Paddick conformity indexes of the two plans were comparable the SCG-optimization with 2 arcs (1 noncoplanar and 1 coplanar) significantly improved the conventional VMAT with 3 arcs (2 noncoplanar and 1 coplanar). Specifically V16 V10 and V5 of the brain were reduced by 11%, 11% and 12% respectively. The beam delivery time was shortened by approximately 30%. Conclusion: The proposed 4pi arc space optimization technique promises to significantly reduce the brain toxicity while greatly improving the treatment efficiency.

SU-F-T-79: Monte Carlo Investigation of Optimizing Parameters for Modulated Electron Arc Therapy

International Nuclear Information System (INIS)

Al Ashkar, E; Eraba, K; Imam, M; Eldib, A; Ma, C

2016-01-01

Purpose: Electron arc therapy provides excellent dose distributions for treating superficial tumors along curved surfaces. However this modality has not received widespread application due to the lack of needed advancement in electron beam delivery, accurate electron dose calculation and treatment plan optimization. The aim of the current work is to investigate possible parameters that can be optimized for electron arc (eARC) therapy. Methods: The MCBEAM code was used to generate phase space files for 6 and 12MeV electron beam energies from a Varian trilogy machine. An Electron Multi-leaf collimator eMLC of 2cm thickness positioned at 82 cm source collimated distance was used in the study. Dose distributions for electron arcs were calculated inside a cylindrical phantom using the MCSIM code. The Cylindrical phantom was constructed with 0.2cm voxels and a 15cm diameter. Electron arcs were delivered with two different approaches. The first approach was to deliver the arc as segments of very small field widths. In this approach we also tested the impact of the segment size and the arc increment angle. The second approach is to deliver the arc as a sum of large fields each covering the whole target as seen from the beam eye view. Results: In considering 90 % as the prescription isodose line, the first approach showed a region of buildup proceeding before the prescription zone. This build up is minimizing with the second approach neglecting need for bolus. The second approach also showed less x-ray contamination. In both approaches the variation of the segment size changed the size and location of the prescription isodose line. The optimization process for eARC could involve interplay between small and large segments to achieve desired coverage. Conclusion: An advanced modulation of eARCs will allow for tailored dose distribution for superficial curved target as with challenging scalp cases

SU-F-T-79: Monte Carlo Investigation of Optimizing Parameters for Modulated Electron Arc Therapy

Energy Technology Data Exchange (ETDEWEB)

Al Ashkar, E; Eraba, K; Imam, M [Azhar university, Nasr City, Cairo (Egypt); Eldib, A; Ma, C [Fox Chase Cancer Center, Philadelphia, PA (United States)

2016-06-15

Purpose: Electron arc therapy provides excellent dose distributions for treating superficial tumors along curved surfaces. However this modality has not received widespread application due to the lack of needed advancement in electron beam delivery, accurate electron dose calculation and treatment plan optimization. The aim of the current work is to investigate possible parameters that can be optimized for electron arc (eARC) therapy. Methods: The MCBEAM code was used to generate phase space files for 6 and 12MeV electron beam energies from a Varian trilogy machine. An Electron Multi-leaf collimator eMLC of 2cm thickness positioned at 82 cm source collimated distance was used in the study. Dose distributions for electron arcs were calculated inside a cylindrical phantom using the MCSIM code. The Cylindrical phantom was constructed with 0.2cm voxels and a 15cm diameter. Electron arcs were delivered with two different approaches. The first approach was to deliver the arc as segments of very small field widths. In this approach we also tested the impact of the segment size and the arc increment angle. The second approach is to deliver the arc as a sum of large fields each covering the whole target as seen from the beam eye view. Results: In considering 90 % as the prescription isodose line, the first approach showed a region of buildup proceeding before the prescription zone. This build up is minimizing with the second approach neglecting need for bolus. The second approach also showed less x-ray contamination. In both approaches the variation of the segment size changed the size and location of the prescription isodose line. The optimization process for eARC could involve interplay between small and large segments to achieve desired coverage. Conclusion: An advanced modulation of eARCs will allow for tailored dose distribution for superficial curved target as with challenging scalp cases.

Verification of dosimetric commissioning accuracy of intensity modulated radiation therapy and volumetric modulated arc therapy delivery using task Group-119 guidelines

Directory of Open Access Journals (Sweden)

Karunakaran Kaviarasu

2017-01-01

Full Text Available Aim: The purpose of this study is to verify the accuracy of the commissioning of intensity-modulated radiation therapy (IMRT and volumetric-modulated arc therapy (VMAT based on the recommendation of the American Association of Physicists in Medicine Task Group 119 (TG-119. Materials and Methods: TG-119 proposes a set of clinical test cases to verify the accuracy of IMRT planning and delivery system. For these test cases, we generated two sets of treatment plans, the first plan using 7–9 IMRT fields and a second plan utilizing two-arc VMAT technique for both 6 MV and 15 MV photon beams. The template plans of TG-119 were optimized and calculated by Varian Eclipse Treatment Planning System (version 13.5. Dose prescription and planning objectives were set according to the TG-119 goals. The point dose (mean dose to the contoured chamber volume at the specified positions/locations was measured using compact (CC-13 ion chamber. The composite planar dose was measured with IMatriXX Evaluation 2D array with OmniPro IMRT Software (version 1.7b. The per-field relative gamma was measured using electronic portal imaging device in a way similar to the routine pretreatment patient-specific quality assurance. Results: Our planning results are compared with the TG-119 data. Point dose and fluence comparison data where within the acceptable confident limit. Conclusion: From the obtained data in this study, we conclude that the commissioning of IMRT and VMAT delivery were found within the limits of TG-119.

Evaluation of volumetric modulated arc therapy for cranial radiosurgery using multiple noncoplanar arcs

International Nuclear Information System (INIS)

Audet, Chantal; Poffenbarger, Brett A.; Chang, Pauling; Jackson, Paul S.; Lundahl, Robert E.; Ryu, Stephen I.; Ray, Gordon R.

2011-01-01

Purpose: To evaluate a commercial volumetric modulated arc therapy (VMAT), using multiple noncoplanar arcs, for linac-based cranial radiosurgery, as well as evaluate the combined accuracy of the VMAT dose calculations and delivery. Methods: Twelve patients with cranial lesions of variable size (0.1-29 cc) and two multiple metastases patients were planned (Eclipse RapidArc AAA algorithm, v8.6.15) using VMAT (1-6 noncoplanar arcs), dynamic conformal arc (DCA, ∼4 arcs), and IMRT (nine static fields). All plans were evaluated according to a conformity index (CI), healthy brain tissue doses and volumes, and the dose to organs at risk. A 2D dose distribution was measured (Varian Novalis Tx, HD120 MLC, 1000 MU/min, 6 MV beam) for the ∼4 arc VMAT treatment plans using calibrated film dosimetry. Results: The CI (0-1 best) average for all plans was best for ∼4 noncoplanar arc VMAT at 0.86 compared with ∼0.78 for IMRT and a single arc VMAT and 0.68 for DCA. The volumes of healthy brain receiving 50% of the prescribed target coverage dose or more (V 50% ) were lowest for the four arc VMAT [RA(4)] and DCA plans. The average ratio of the V 50% for the other plans to the RA(4) V 50% were 1.9 for a single noncoplanar arc VMAT [RA(1nc)], 1.4 for single full coplanar arc VMAT [RA(1f)] and 1.3 for IMRT. The V 50% improved significantly for single isocenter multiple metastases plan when two noncoplanar VMAT arcs were added to a full single coplanar one. The maximum dose to 5 cc of the outer 1 cm rim of healthy brain which one may want to keep below nonconsequential doses of 300-400 cGy, was 2-3 times greater for IMRT, RA(1nc) and RA(1f) plans compared with the multiple noncoplanar arc DCA and RA(4) techniques. Organs at risk near (0-4 mm) to targets were best spared by (i) single noncoplanar arcs when the targets are lateral to the organ at risk and (ii) by skewed nonvertical planes of IMRT fields when the targets are not lateral to the organ at risk. The highest dose gradient

A practical method of modeling a treatment couch using cone-beam computed tomography for intensity-modulated radiation therapy and RapidArc treatment delivery

Energy Technology Data Exchange (ETDEWEB)

Aldosary, Ghada, E-mail: ghada.aldosary@mail.mcgill.ca [Medical Physics Unit, McGill University Health Centre, Montreal, Quebec (Canada); Nobah, Ahmad; Al-Zorkani, Faisal [Biomedical Physics Department, King Faisal Specialist Hospital and Research Center, Riyadh (Saudi Arabia); Devic, Slobodan [Department of Radiation Oncology, Jewish General Hospital, McGill University, Montreal, Quebec (Canada); Moftah, Belal [Medical Physics Unit, McGill University Health Centre, Montreal, Quebec (Canada); Biomedical Physics Department, King Faisal Specialist Hospital and Research Center, Riyadh (Saudi Arabia)

2015-01-01

The effect of a treatment couch on dose perturbation is not always fully considered in intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). In the course of inverse planning radiotherapy techniques, beam parameter optimization may change in the absence of the couch, causing errors in the calculated dose distributions. Although modern treatment planning systems (TPS) include data for the treatment couch components, they are not manufactured identically. Thus, variations in their Hounsfield unit (HU) values may exist. Moreover, a radiotherapy facility may wish to have a third-party custom tabletop installed that is not included by the TPS vendor. This study demonstrates a practical and simple method of acquiring reliable computed tomography (CT) data for the treatment couch and shows how the absorbed dose calculated with the modeled treatment couch can differ from that with the default treatment couch found in the TPS. We also experimentally verified that neglecting to incorporate the treatment couch completely in the treatment planning process might result in dose differences of up to 9.5% and 7.3% for 4-MV and 10-MV photon beams, respectively. Furthermore, 20 RapidArc and IMRT cases were used to quantify the change in calculated dose distributions caused by using either the default or modeled couch. From 2-dimensional (2D) ionization chamber array measurements, we observed large dose distribution differences between the measurements and calculations when the couch was omitted that varied according to the planning technique and anatomic site. Thus, incorporating the treatment couch in the dose calculation phase of treatment planning significantly decreases dose calculation errors.

The diagnostic neutral beam injector with arc-discharge plasma source on the TCV Tokamak

Energy Technology Data Exchange (ETDEWEB)

Karpushov, Alexander N. [Ecole Polytechnique Federale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas, Association Euratom-Confederation Suisse, CH-1015 Lausanne (Switzerland)], E-mail: alexander.karpushov@epfl.ch; Andrebe, Yanis; Duval, Basil P.; Bortolon, Alessandro [Ecole Polytechnique Federale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas, Association Euratom-Confederation Suisse, CH-1015 Lausanne (Switzerland)

2009-06-15

The diagnostic neutral beam injector (DNBI) together with a charge exchange recombination spectroscopy (CXRS) system has been used on the TCV Tokamak as a diagnostic tool for local measurements of plasma ion temperature, velocity and carbon impurity density based on analysis of the beam induced impurity radiation emission since 2000. To improve the performance of the CXRS diagnostic, several upgrades of both the optical system and the neutral beam were performed. An increase of the plasma source size together with beam optimization in 2003 resulted in a twofold increase the beam current. The RF plasma generator was replaced by an arc-discharge plasma source together with a new ion optical system (IOS) in 2006 and subsequent beam optimization is presented herein. This was designed to increase the line brightness of the beam in the CXRS observation region without increasing of the injected power (to avoid plasma perturbation by the beam). The beam characteristics are measured by a multi-chord scanning of Doppler-shifted H{sub {alpha}} emission, thermal measurements on a movable calorimeter and visible optical measurements inside the Tokamak vessel.

Arcing and rf signal generation during target irradiation by a high-energy, pulsed neutral particle beam

International Nuclear Information System (INIS)

Robiscoe, R.T.

1988-02-01

We present a theory describing the dynamics of arc discharges in bulk dielectric materials on board space-based vehicles. Such ''punch-through'' arcs can occur in target satellites irradiated by high-energy (250 MeV), pulsed (100 mA x 10 ms) neutral particle beams. We treat the arc as a capacitively limited avalanche current in the target dielectric material, and we find expressions for the arc duration, charge transport, currents, and discharge energy. These quantities are adjusted to be consistent with known scaling laws for the area of charge depleted by the arc. After a brief account of the statistical distribution of voltages at which the arc starts and stops, we calculate the signal strength and frequency spectrum of the electromagnetic radiation broadcast by the arc. We find that arcs from thick (/similar to/1 cm) targets can generate rf signals detectable up to 1000 km from the target, bu a radio receiver operating at frequency 80 MHz, bandwidth 100 kHz, and detection threshold -105 dBm. These thick-target arc signals are 10 to 20 dB above ambient noise at the receiver, and they provide target hit assessment if the signal spectrum can be sampled at several frequencies in the nominal range 30-200 MHz. Thin-target (/similar to/1 mm) arc signals are much weaker, but when they are detecable in conjunction with thick-target signals, target discrimination is possible by comparing the signal frequency spectra. 24 refs., 12 figs

SU-E-T-403: Evaluation of the Beam Performance of a Varian TrueBeam Linear Accelerator Under External Device-Based Gated Delivery Conditions

International Nuclear Information System (INIS)

Kobulnicky, K; Pawlak, D; Purwar, A

2015-01-01

Purpose: To examine the beam performance of a Varian TrueBeam linear accelerator under external device-based gated delivery conditions. Methods: Six gating cycles were used to evaluate the gating performance of a standard production TrueBeam system that was not specially tuned in any way. The system was equipped with a factory installed external gating interface (EXGI). An in-house EXGI tester box was used to simulate the input gating signals. The gating cycles were selected based on long beam-on and short beam-off times, short beam-on and long beam-off times, or equal beam on and off times to check linac performance. The beam latencies were measured as the time difference between the logic high gating signal and the first or last target pulses with an oscilloscope. Tissue-Phantom Ratio, beam flatness, and dose distributions from 5 different plans were measured using the 6 different gating durations and the un-gated irradiation. A PTW 729 2-D array was used to compare 5 plans versus the un-gated delivery with a 1%/1mm gamma index passing criteria. Results: The beam latencies of the linac were based off of 20 samples for beam-on and beam-off, for each gating cycle. The average beam-on delays were measured to be between 57 and 66msec, with a maximum of 88 msec. The beam off latencies averaged between 19 and 26msec, with a maximum of 48 msec. TPR20,10 measurements showed beam energy stability within 0.5% of the un-gated delivery. Beam flatness was better than 2.5% for all gated cycles. All but two deliveries, the open field with 4 seconds on, 1 second off, and a five field IMRT plan with 0.5 seconds on, 2.5 seconds off, had >90% passing rate. Conclusion: TrueBeam demonstrates excellent beam stability with minimal beam latencies under external device-based gated operations. Dosimetric measurements show minimal variation in beam energy, flatness, and plan delivery. Authors are employees of Varian Medical Systems, Inc

SU-E-T-403: Evaluation of the Beam Performance of a Varian TrueBeam Linear Accelerator Under External Device-Based Gated Delivery Conditions

Energy Technology Data Exchange (ETDEWEB)

Kobulnicky, K; Pawlak, D; Purwar, A [Varian Medical Systems, Inc., Palo Alto, CA (United States)

2015-06-15

Purpose: To examine the beam performance of a Varian TrueBeam linear accelerator under external device-based gated delivery conditions. Methods: Six gating cycles were used to evaluate the gating performance of a standard production TrueBeam system that was not specially tuned in any way. The system was equipped with a factory installed external gating interface (EXGI). An in-house EXGI tester box was used to simulate the input gating signals. The gating cycles were selected based on long beam-on and short beam-off times, short beam-on and long beam-off times, or equal beam on and off times to check linac performance. The beam latencies were measured as the time difference between the logic high gating signal and the first or last target pulses with an oscilloscope. Tissue-Phantom Ratio, beam flatness, and dose distributions from 5 different plans were measured using the 6 different gating durations and the un-gated irradiation. A PTW 729 2-D array was used to compare 5 plans versus the un-gated delivery with a 1%/1mm gamma index passing criteria. Results: The beam latencies of the linac were based off of 20 samples for beam-on and beam-off, for each gating cycle. The average beam-on delays were measured to be between 57 and 66msec, with a maximum of 88 msec. The beam off latencies averaged between 19 and 26msec, with a maximum of 48 msec. TPR20,10 measurements showed beam energy stability within 0.5% of the un-gated delivery. Beam flatness was better than 2.5% for all gated cycles. All but two deliveries, the open field with 4 seconds on, 1 second off, and a five field IMRT plan with 0.5 seconds on, 2.5 seconds off, had >90% passing rate. Conclusion: TrueBeam demonstrates excellent beam stability with minimal beam latencies under external device-based gated operations. Dosimetric measurements show minimal variation in beam energy, flatness, and plan delivery. Authors are employees of Varian Medical Systems, Inc.

The accuracy evaluation according to dose delivery interruption and restart for volumetric modulated arc therapy

Energy Technology Data Exchange (ETDEWEB)

Lee, Dong Hyung; Bae, Sun Myung; Kwak, Jung Won; Kang, Tae Young; Bck, Geum Mun [Dept. of Radiation Oncology, Asan Medical Center, Seoul(Korea, Republic of)

2013-03-15

The accurate movement of gantry rotation, collimator and correct application of dose rate are very important to approach the successful performance of Volumetric Modulated Arc Therapy (VMAT), because it is tightly interlocked with a complex treatment plan. The interruption and restart of dose delivery, however, are able to occur on treatment by various factors of a treatment machine and treatment plan. If unexpected problems of a treat machine or a patient interrupt the VMAT, the movement of treatment machine for delivering the remaining dose will be restarted at the start point. In this investigation, We would like to know the effect of interruptions and restart regarding dose delivery at VMAT. Treatment plans of 10 patients who had been treated at our center were used to measure and compare the dose distribution of each VMAT after converting to a form of digital image and communications in Medicine (DICOM) with treatment planning system (Eclipse V 10.0, Varian, USA). We selected the 6 MV photon energy of Trilogy (Varian, USA) and used OmniPro I'mRT system (V 1.7b, IBA dosimetry, Germany) to analyze the data that were acquired through this measurement with two types of interruptions four times for each case. The door interlock and the beam-off were used to stop and then to restart the dose delivery of VMAT. The gamma index in OmniPro I'mRT system and T-test in Microsoft Excel 2007 were used to evaluate the result of this investigation. The deviations of average gamma index in cases with door interlock, beam-off and without interruption on VMAT are 0.141, 0.128 and 0.1. The standard deviations of acquired gamma values are 0.099, 0.091, 0.071 and The maximum gamma value in each case is 0.413, 0.379, 0.286, respectively. This analysis has a 95-percent confidence level and the P-value of T-test is under 0.05. Gamma pass rate (3%, 3 mm) is acceptable in all of measurements. As a result, We could make sure that the interruption of this investgation are not

Dose verification for respiratory-gated volumetric modulated arc therapy

Energy Technology Data Exchange (ETDEWEB)

Qian Jianguo; Xing Lei; Liu Wu; Luxton, Gary, E-mail: gluxton@stanford.edu [Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305 (United States)

2011-08-07

A novel commercial medical linac system (TrueBeam(TM), Varian Medical Systems, Palo Alto, CA) allows respiratory-gated volumetric modulated arc therapy (VMAT), a new modality for treating moving tumors with high precision and improved accuracy by allowing for regular motion associated with a patient's breathing during VMAT delivery. The purpose of this work is to adapt a previously-developed dose reconstruction technique to evaluate the fidelity of VMAT treatment during gated delivery under clinic-relevant periodic motion related to patient breathing. A Varian TrueBeam system was used in this study. VMAT plans were created for three patients with lung or pancreas tumors. Conventional 6 and 15 MV beams with flattening filter and high-dose-rate 10 MV beams with no flattening filter were used in these plans. Each patient plan was delivered to a phantom first without gating and then with gating for three simulated respiratory periods (3, 4.5 and 6 s). Using the adapted log-file-based dose reconstruction procedure supplemented with ion chamber array (Seven29(TM), PTW, Freiburg, Germany) measurements, the delivered dose was used to evaluate the fidelity of gated VMAT delivery. Comparison of Seven29 measurements with and without gating showed good agreement with gamma-index passing rates above 99% for 1%/1 mm dose accuracy/distance-to-agreement criteria. With original plans as reference, gamma-index passing rates were 100% for the reconstituted plans (1%/1 mm criteria) and 93.5-100% for gated Seven29 measurements (3%/3 mm criteria). In the presence of leaf error deliberately introduced into the gated delivery of a pancreas patient plan, both dose reconstruction and Seven29 measurement consistently indicated substantial dosimetric differences from the original plan. In summary, a dose reconstruction procedure was demonstrated for evaluating the accuracy of respiratory-gated VMAT delivery. This technique showed that under clinical operation, the TrueBeam system

Beam Delivery Simulation: BDSIM - Development & Optimization

CERN Document Server

Nevay, Laurence James; Garcia-Morales, H; Gibson, S M; Kwee-Hinzmann, R; Snuverink, J; Deacon, L C

2014-01-01

Beam Delivery Simulation (BDSIM) is a Geant4 and C++ based particle tracking code that seamlessly tracks particles through accelerators and detectors, including the full range of particle interaction physics processes from Geant4. BDSIM has been successfully used to model beam loss and background conditions for many current and future linear accelerators such as the Accelerator Test Facility 2 (ATF2) and the International Linear Collider (ILC). Current developments extend its application for use with storage rings, in particular for the Large Hadron Collider (LHC) and the High Luminosity upgrade project (HL-LHC). This paper presents the latest results from using BDSIM to model the LHC as well as the developments underway to improve performance.

Variable dose rate single-arc IMAT delivered with a constant dose rate and variable angular spacing

International Nuclear Information System (INIS)

Tang, Grace; Earl, Matthew A; Yu, Cedric X

2009-01-01

Single-arc intensity-modulated arc therapy (IMAT) has gained worldwide interest in both research and clinical implementation due to its superior plan quality and delivery efficiency. Single-arc IMAT techniques such as the Varian RapidArc(TM) deliver conformal dose distributions to the target in one single gantry rotation, resulting in a delivery time in the order of 2 min. The segments in these techniques are evenly distributed within an arc and are allowed to have different monitor unit (MU) weightings. Therefore, a variable dose-rate (VDR) is required for delivery. Because the VDR requirement complicates the control hardware and software of the linear accelerators (linacs) and prevents most existing linacs from delivering IMAT, we propose an alternative planning approach for IMAT using constant dose-rate (CDR) delivery with variable angular spacing. We prove the equivalence by converting VDR-optimized RapidArc plans to CDR plans, where the evenly spaced beams in the VDR plan are redistributed to uneven spacing such that the segments with larger MU weighting occupy a greater angular interval. To minimize perturbation in the optimized dose distribution, the angular deviation of the segments was restricted to ≤± 5 deg. This restriction requires the treatment arc to be broken into multiple sectors such that the local MU fluctuation within each sector is reduced, thereby lowering the angular deviation of the segments during redistribution. The converted CDR plans were delivered with a single gantry sweep as in the VDR plans but each sector was delivered with a different value of CDR. For four patient cases, including two head-and-neck, one brain and one prostate, all CDR plans developed with the variable spacing scheme produced similar dose distributions to the original VDR plans. For plans with complex angular MU distributions, the number of sectors increased up to four in the CDR plans in order to maintain the original plan quality. Since each sector was

Can volumetric modulated arc therapy with flattening filter free beams play a role in stereotactic body radiotherapy for liver lesions? A volume-based analysis

International Nuclear Information System (INIS)

Reggiori, Giacomo; Mancosu, Pietro; Castiglioni, Simona; Alongi, Filippo; Pellegrini, Chiara; Lobefalo, Francesca; Catalano, Maddalena; Fogliata, Antonella; Arcangeli, Stefano; Navarria, Piera; Cozzi, Luca; Scorsetti, Marta

2012-01-01

Purpose: To compare volumetric modulated arc therapy with flattening filter free (FFF) and flattening filter (FF) beams in patients with hepatic metastases subject to hypofractionated radiotherapy (RT). Methods: A planning study on 13 virtual lesions of increasing volume was performed. Two single arc plans were optimized with the RapidArc technique using either FFF or FF beams. A second planning study was performed on ten patients treated for liver metastases to validate conclusions. In all cases, a dose of 75 Gy in 3 fractions was prescribed to the planning target volume (PTV) and plans were evaluated in terms of coverage, homogeneity, conformity, mean dose to healthy liver and to healthy tissue. For each parameter, results were expressed in relative terms as the percentage ratio between FFF and FF data. Results: In terms of PTV coverage, conformity index favored FFF for targets of intermediate size while FF resulted more suitable for small ( 3 ) and large (>300 cm 3 ) targets. Plans optimized with FFF beams resulted in increased sparing of healthy tissue in ≅85% of cases. Despite the qualitative results, no statistically significant differences were found between FFF and FF results. Plans optimized with un-flattened beams resulted in higher average MU/Gy than plans with FF beams. A remarkable and significant difference was observed in the beam-on time (BOT) needed to deliver plans. The BOT for FF plans was 8.2 ± 1.0 min; for FFF plans BOT was 2.2 ± 0.2 min. Conclusions: RapidArc plans optimized using FFF were dosimetrically equivalent to those optimized using FF beams, showing the feasibility of SBRT treatments with FFF beams. Some improvement in healthy tissue sparing was observed when using the FFF modality due to the different beam's profile. The main advantage was a considerable reduction of beam-on time, relevant for SBRT techniques.

Volumetric Modulated Arc-Based Hypofractionated Stereotactic Radiotherapy for the Treatment of Selected Intracranial Arteriovenous Malformations: Dosimetric Report and Early Clinical Experience

Energy Technology Data Exchange (ETDEWEB)

Subramanian, Sai; Srinivas, Chilukuri; Ramalingam, K.; Babaiah, M.; Swamy, S. Thirumalai; Arun, G.; Kathirvel, M.; Ashok, S. [Yashoda Super Specialty Hospital, Hyderabad (India); Clivio, Alessandro [Oncology Institute of Southern Switzerland, Bellinzona (Switzerland); Fogliata, Antonella, E-mail: antonella.fogliata-cozzi@eoc.ch [Oncology Institute of Southern Switzerland, Bellinzona (Switzerland); Nicolini, Giorgia [Oncology Institute of Southern Switzerland, Bellinzona (Switzerland); Rao, K. Srinivasa; Reddy, T. Pratap; Amit, Jotwani [Yashoda Super Specialty Hospital, Hyderabad (India); Vanetti, Eugenio; Cozzi, Luca [Oncology Institute of Southern Switzerland, Bellinzona (Switzerland)

2012-03-01

Purpose: To evaluate, with a dosimetric and clinical feasibility study, RapidArc (a volumetric modulated arc technique) for hypofractionated stereotactic radiotherapy treatment of large arteriovenous malformations (AVMs). Methods and Materials: Nine patients were subject to multimodality imaging (magnetic resonance, computed tomography, and digital subtraction angiography) to determine nidus and target volumes, as well as involved organs at risk (optical structures, inner ear, brain stem). Plans for multiple intensity-modulated arcs with a single isocenter were optimized for a fractionation of 25 Gy in 5 fractions. All plans were optimized for 6-MV photon beams. Dose-volume histograms were analyzed to assess plan quality. Delivery parameters were reported to appraise technical features of RapidArc, and pretreatment quality assurance measurements were carried out to report on quality of delivery. Results: Average size of AVM nidus was 26.2 cm{sup 3}, and RapidArc plans provided complete target coverage with minimal overdosage (V{sub 100%} = 100% and V{sub 110%} < 1%) and excellent homogeneity (<6%). Organs at risk were highly spared. The D{sub 1%} to chiasm, eyes, lenses, optic nerves, and brainstem (mean {+-} SD) was 6.4 {+-} 8.3, 1.9 {+-} 3.8, 2.3 {+-} 2.2, 0.7 {+-} 0.9, 4.4 {+-} 7.2, 12.2 {+-} 9.6 Gy, respectively. Conformity index (CI{sub 95%}) was 2.2 {+-} 0.1. The number of monitor units per gray was 277 {+-} 45, total beam-on time was 2.5 {+-} 0.3 min. Planning vs. delivery {gamma} pass rate was 98.3% {+-} 0.9%. None of the patients developed acute toxicity. With a median follow-up of 9 months, 3 patients presented with deterioration of symptoms and were found to have postradiation changes but responded symptomatically to steroids. These patients continue to do well on follow-up. One patient developed headache and seizures, which was attributed to intracranial bleed, confirmed on imaging. Conclusion: Hypofractionated stereotactic radiotherapy can be

Tumor cell survival dependence on helical tomotherapy, continuous arc and segmented dose delivery

International Nuclear Information System (INIS)

Yang Wensha; Wang Li; Larner, James; Read, Paul; Benedict, Stan; Sheng Ke

2009-01-01

The temporal pattern of radiation delivery has been shown to influence the tumor cell survival fractions for the same radiation dose. To study the effect more specifically for state of the art rotational radiation delivery modalities, 2 Gy of radiation dose was delivered to H460 lung carcinoma, PC3 prostate cancer cells and MCF-7 breast tumor cells by helical tomotherapy (HT), seven-field LINAC (7F), and continuous dose delivery (CDD) over 2 min that simulates volumetric rotational arc therapy. Cell survival was measured by the clonogenic assay. The number of viable H460 cell colonies was 23.2 ± 14.4% and 27.7 ± 15.6% lower when irradiated by CDD compared with HT and 7F, respectively, and the corresponding values were 36.8 ± 18.9% and 35.3 ± 18.9% lower for MCF7 cells (p < 0.01). The survival of PC3 was also lower when irradiated by CDD than by HT or 7F but the difference was not as significant (p = 0.06 and 0.04, respectively). The higher survival fraction from HT delivery was unexpected because 90% of the 2 Gy was delivered in less than 1 min at a significantly higher dose rate than the other two delivery techniques. The results suggest that continuous dose delivery at a constant dose rate results in superior in vitro tumor cell killing compared with prolonged, segmented or variable dose rate delivery.

Letter to the Editor on 'Single-Arc IMRT?'.

Science.gov (United States)

Otto, Karl

2009-04-21

In the note 'Single Arc IMRT?' (Bortfeld and Webb 2009 Phys. Med. Biol. 54 N9-20), Bortfeld and Webb present a theoretical investigation of static gantry IMRT (S-IMRT), single-arc IMRT and tomotherapy. Based on their assumptions they conclude that single-arc IMRT is inherently limited in treating complex cases without compromising delivery efficiency. Here we present an expansion of their work based on the capabilities of the Varian RapidArc single-arc IMRT system. Using the same theoretical framework we derive clinically deliverable single-arc IMRT plans based on these specific capabilities. In particular, we consider the range of leaf motion, the ability to rapidly and continuously vary the dose rate and the choice of collimator angle used for delivery. In contrast to the results of Bortfeld and Webb, our results show that single-arc IMRT plans can be generated that closely match the theoretical optimum. The disparity in the results of each investigation emphasizes that the capabilities of the delivery system, along with the ability of the optimization algorithm to exploit those capabilities, are of particular importance in single-arc IMRT. We conclude that, given the capabilities available with the RapidArc system, single-arc IMRT can produce complex treatment plans that are delivered efficiently (in approximately 2 min).

The relation of electrode voltages to charge position in SLC arc and final focus beam position monitors

International Nuclear Information System (INIS)

Fordham, C.

1989-01-01

The position of a charged particle beam can be measured with a Beam Position Monitor (BPM) by converting the voltages induced on its array of electrodes into a position offset from the array's center. Most of the BPMs in the Arcs and Final Focus of the SLC use four stripline electrodes arranged symmetrically around the beam; normalized voltage differences are calculated as the difference divided by the sum of voltages on opposite electrode pairs. The resulting number is multiplied by a conversion factor, denoted in this paper as S b , to give the offset (in millimeters) of the charge from the center of the BPM. Prior to installation in the beam line, the BPMs were calibrated with a charge pulse on a rod. Owing to geometric effects which will be discussed later, a different conversion factor had to be used for calibration. It will be denoted here by S r . This paper gives the results of calculations and measurements of S r and S b for Arc and Final Focus BPMs. This paper also describes the relevant physical properties of the several types of BPMs and calculations of the expected scale factors, the measurement methods used, and gives the results of measurements, which are compared with the theoretical expectations. 2 refs., 18 figs., 7 tabs

TH-AB-201-12: Using Machine Log-Files for Treatment Planning and Delivery QA

Energy Technology Data Exchange (ETDEWEB)

Stanhope, C [Beaumont Health System, Royal Oak MI and Wayne State University, Detroit, MI (United States); Liang, J; Drake, D; Yan, D [Beaumont Health System, Royal Oak, MI (United States)

2016-06-15

Purpose: To determine the segment reduction and dose resolution necessary for machine log-files to effectively replace current phantom-based patient-specific quality assurance, while minimizing computational cost. Methods: Elekta’s Log File Convertor R3.2 records linac delivery parameters (dose rate, gantry angle, leaf position) every 40ms. Five VMAT plans [4 H&N, 1 Pulsed Brain] comprised of 2 arcs each were delivered on the ArcCHECK phantom. Log-files were reconstructed in Pinnacle on the phantom geometry using 1/2/3/4° control point spacing and 2/3/4mm dose grid resolution. Reconstruction effectiveness was quantified by comparing 2%/2mm gamma passing rates of the original and log-file plans. Modulation complexity scores (MCS) were calculated for each beam to correlate reconstruction accuracy and beam modulation. Percent error in absolute dose for each plan-pair combination (log-file vs. ArcCHECK, original vs. ArcCHECK, log-file vs. original) was calculated for each arc and every diode greater than 10% of the maximum measured dose (per beam). Comparing standard deviations of the three plan-pair distributions, relative noise of the ArcCHECK and log-file systems was elucidated. Results: The original plans exhibit a mean passing rate of 95.1±1.3%. The eight more modulated H&N arcs [MCS=0.088±0.014] and two less modulated brain arcs [MCS=0.291±0.004] yielded log-file pass rates most similar to the original plan when using 1°/2mm [0.05%±1.3% lower] and 2°/3mm [0.35±0.64% higher] log-file reconstructions respectively. Log-file and original plans displayed percent diode dose errors 4.29±6.27% and 3.61±6.57% higher than measurement. Excluding the phantom eliminates diode miscalibration and setup errors; log-file dose errors were 0.72±3.06% higher than the original plans – significantly less noisy. Conclusion: For log-file reconstructed VMAT arcs, 1° control point spacing and 2mm dose resolution is recommended, however, less modulated arcs may allow less

Underwater cladding with laser beam and plasma arc welding

International Nuclear Information System (INIS)

White, R.A.; Fusaro, R.; Jones, M.G.; Solomon, H.D.; Milian-Rodriguez, R.R.

1997-01-01

Two welding processes, plasma arc (transferred arc) (PTA) and laser beam, were investigated to apply cladding to austenitic stainless steels and Inconel 600. These processes have long been used to apply cladding layers , but the novel feature being reported here is that these cladding layers were applied underwater, with a water pressure equivalent to 24 m (80 ft). Being able to apply the cladding underwater is very important for many applications, including the construction of off-shore oil platforms and the repair of nuclear reactors. In the latter case, being able to weld underwater eliminates the need for draining the reactor and removing the fuel. Welding underwater in reactors presents numerous challenges, but the ability to weld without having to drain the reactor and remove the fuel provides a huge cost savings. Welding underwater in reactors must be done remotely, but because of the radioactive corrosion products and neutron activation of the steels, remote welding would also be required even if the reactor is drained and the fuel removed. In fact, without the shielding of the water, the remote welding required if the reactor is drained might be even more difficult than that required with underwater welds. Furthermore, as shall be shown, the underwater welds that the authors have made were of high quality and exhibit compressive rather than tensile residual stresses

Continuous Arc Rotation of the Couch Therapy for the Delivery of Accelerated Partial Breast Irradiation: A Treatment Planning Analysis

International Nuclear Information System (INIS)

Shaitelman, Simona F.; Kim, Leonard H.; Yan Di; Martinez, Alvaro A.; Vicini, Frank A.; Grills, Inga S.

2011-01-01

Purpose: We present a novel form of arc therapy: continuous arc rotation of the couch (C-ARC) and compare its dosimetry with three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT), and volumetric-modulated arc therapy (VMAT) for accelerated partial breast irradiation (APBI). C-ARC, like VMAT, uses a modulated beam aperture and dose rate, but with the couch, not the gantry, rotating. Methods and Materials: Twelve patients previously treated with APBI using 3D-CRT were replanned with (1) C-ARC, (2) IMRT, and (3) VMAT. C-ARC plans were designed with one medial and one lateral arc through which the couch rotated while the gantry was held stationary at a tangent angle. Target dose coverage was normalized to the 3D-CRT plan. Comparative endpoints were dose to normal breast tissue, lungs, and heart and monitor units prescribed. Results: Compared with 3D-CRT, C-ARC, IMRT, and VMAT all significantly reduced the ipsilateral breast V50% by the same amount (mean, 7.8%). Only C-ARC and IMRT plans significantly reduced the contralateral breast maximum dose, the ipsilateral lung V5Gy, and the heart V5%. C-ARC used on average 40%, 30%, and 10% fewer monitor units compared with 3D-CRT, IMRT, and VMAT, respectively. Conclusions: C-ARC provides improved dosimetry and treatment efficiency, which should reduce the risks of toxicity and secondary malignancy. Its tangent geometry avoids irradiation of critical structures that is unavoidable using the en face geometry of VMAT.

Transverse emittance-preserving arc compressor for high-brightness electron beam-based light sources and colliders

Science.gov (United States)

Di Mitri, S.; Cornacchia, M.

2015-03-01

Bunch length magnetic compression is used in high-brightness linacs driving free-electron lasers (FELs) and particle colliders to increase the peak current of the injected beam. To date, it is performed in dedicated insertions made of few degrees bending magnets and the compression factor is limited by the degradation of the beam transverse emittance owing to emission of coherent synchrotron radiation (CSR). We reformulate the known concept of CSR-driven optics balance for the general case of varying bunch length and demonstrate, through analytical and numerical results, that a 500 pC charge beam can be time-compressed in a periodic 180 deg arc at 2.4 GeV beam energy and lower, by a factor of up to 45, reaching peak currents of up to 2 kA and with a normalized emittance growth at the 0.1 μ \\text{m} rad level. The proposed solution offers new schemes of beam longitudinal gymnastics; an application to an energy recovery linac driving FEL is discussed.

Technical Note: Using experimentally determined proton spot scanning timing parameters to accurately model beam delivery time.

Science.gov (United States)

Shen, Jiajian; Tryggestad, Erik; Younkin, James E; Keole, Sameer R; Furutani, Keith M; Kang, Yixiu; Herman, Michael G; Bues, Martin

2017-10-01

To accurately model the beam delivery time (BDT) for a synchrotron-based proton spot scanning system using experimentally determined beam parameters. A model to simulate the proton spot delivery sequences was constructed, and BDT was calculated by summing times for layer switch, spot switch, and spot delivery. Test plans were designed to isolate and quantify the relevant beam parameters in the operation cycle of the proton beam therapy delivery system. These parameters included the layer switch time, magnet preparation and verification time, average beam scanning speeds in x- and y-directions, proton spill rate, and maximum charge and maximum extraction time for each spill. The experimentally determined parameters, as well as the nominal values initially provided by the vendor, served as inputs to the model to predict BDTs for 602 clinical proton beam deliveries. The calculated BDTs (T BDT ) were compared with the BDTs recorded in the treatment delivery log files (T Log ): ∆t = T Log -T BDT . The experimentally determined average layer switch time for all 97 energies was 1.91 s (ranging from 1.9 to 2.0 s for beam energies from 71.3 to 228.8 MeV), average magnet preparation and verification time was 1.93 ms, the average scanning speeds were 5.9 m/s in x-direction and 19.3 m/s in y-direction, the proton spill rate was 8.7 MU/s, and the maximum proton charge available for one acceleration is 2.0 ± 0.4 nC. Some of the measured parameters differed from the nominal values provided by the vendor. The calculated BDTs using experimentally determined parameters matched the recorded BDTs of 602 beam deliveries (∆t = -0.49 ± 1.44 s), which were significantly more accurate than BDTs calculated using nominal timing parameters (∆t = -7.48 ± 6.97 s). An accurate model for BDT prediction was achieved by using the experimentally determined proton beam therapy delivery parameters, which may be useful in modeling the interplay effect and patient throughput. The model may

A delivery transfer function (DTF) analysis for helical tomotherapy

International Nuclear Information System (INIS)

Kissick, Michael W; Mackie, Thomas Rockwell; Jeraj, Robert

2007-01-01

The previous theoretical work of a delivery transfer function (DTF) in radiotherapy is expanded to include the unique intensity modulation method of helical tomotherapy. In addition to the collimation of each beamlet, and the Gaussian scatter convolution spreading of the dose that other radiotherapy units have, helical tomotherapy uses 51 small arcs of varying lengths to adjust the intensity. The blurring from these arcs is not taken into account during treatment planning. A theoretical DTF is constructed, and a calculation is performed which includes this unique source motion in relation to the other DTF components. Various typical delivery parameters are used to generate resolution maps for a constant intensity projection. Near the isocenter, the transverse (to a given beam direction) blurring is small but at larger radii (>6 cm), the source blurring dominates over leaf size. For most clinical situations, this inherent source motion blurring is expected to be negligible

Asymmetric fan beams (AFB) for improvement of the craniocaudal dose distribution in helical tomotherapy delivery

International Nuclear Information System (INIS)

Gladwish, Adam; Kron, Tomas; McNiven, Andrea; Bauman, Glenn; Van Dyk, Jake

2004-01-01

Helical tomotherapy (HT) is a novel radiotherapy technique that utilizes intensity modulated fan beams that deliver highly conformal dose distributions in a helical beam trajectory. The most significant limitation in dose delivery with a constant fan beam thickness (FBT) is the penumbra width of the dose distribution in the craniocaudal direction, which is equivalent to the FBT. We propose to employ a half-blocked fan beam at start and stop location to reduce the penumbra width by half. By opening the jaw slowly during the helical delivery until the desired FBT is achieved it is possible to create a sharper edge in the superior and inferior direction from the target. The technique was studied using a tomotherapy beam model implemented on a commercial treatment planning system (Theraplan Plus V3.0). It was demonstrated that the dose distribution delivered using a 25 mm fan beam can be improved significantly, to reduce the dose to normal structures located superiorly and inferiorly of the target. Dosimetry for this technique is straightforward down to a FBT of 15 mm and implementation should be simple as no changes in couch movement are required compared to a standard HT delivery. We conclude that the use of asymmetric collimated fan beams for the start and stop of the helical tomotherapeutic dose delivery has the potential of significantly improving the dose distribution in helical tomotherapy

TECHNOLOGIES FOR DELIVERY OF PROTON AND ION BEAMS FOR RADIOTHERAPY

CERN Document Server

Owen, H; Alonso, J; Mackay, R

2014-01-01

Recent developments for the delivery of proton and ion beam therapy have been significant, and a number of technological solutions now exist for the creation and utilisation of these particles for the treatment of cancer. In this paper we review the historical development of particle accelerators used for external beam radiotherapy and discuss the more recent progress towards more capable and cost-effective sources of particles.

Laser beam uniformity and stability using homogenizer-based fiber optic launch method: square core fiber delivery

Science.gov (United States)

Lizotte, Todd E.

2011-03-01

Over the years, technological achievements within the laser medical diagnostic, treatment, and therapy markets have led to ever increasing requirements for greater control of critical laser beam parameters. Increased laser power/energy stabilization, temporal and spatial beam shaping and flexible laser beam delivery systems with ergonomic focusing or imaging lens systems are sought by leading medical laser system producers. With medical procedures that utilize laser energy, there is a constant emphasis on reducing adverse effects that come about by the laser itself or its optical system, but even when these variables are well controlled the medical professional will still need to deal with the multivariate nature of the human body. Focusing on the variables that can be controlled, such as accurate placement of the laser beam where it will expose a surface being treated as well as laser beam shape and uniformity is critical to minimizing adverse conditions. This paper covers the use of fiber optic beam delivery as a means of defining the beam shape (intensity/power distribution uniformity) at the target plane as well as the use of fiber delivery as a means to allow more flexible articulation of the laser beam over the surface being treated. The paper will present a new concept of using a square core fiber beam delivery design utilizing a unique micro lens array (MLA) launch method that improves the overall stability of the system, by minimizing the impact of the laser instability. The resulting performance of the prototype is presented to demonstrate its stability in comparison to simple lens launch techniques, with an emphasis on homogenization and articulated fiber delivery.

Volumetric modulated arc therapy for delivery of hypofractionated stereotactic lung radiotherapy: A dosimetric and treatment efficiency analysis

International Nuclear Information System (INIS)

McGrath, Samuel D.; Matuszak, Martha M.; Yan Di; Kestin, Larry L.; Martinez, Alvaro A.; Grills, Inga S.

2010-01-01

Purpose/objective(s): Volumetric modulated arc therapy (VMAT) allows for intensity-modulated radiation delivery during gantry rotation with dynamic MLC motion, variable dose rates and gantry speed modulation. We compared VMAT plans with 3D-CRT for hypofractionated lung radiotherapy. Materials/methods: Twenty-one 3D-CRT plans for Stage IA lung cancer previously treated stereotactically were selected. VMAT plans were generated by optimizing machine aperture shape and radiation intensity at 10 deg. intervals. A partial arc range of 180 deg. was manually selected to coincide with tumor location. The arc was resampled down to 5 deg. intervals to ensure dose calculation accuracy. Identical planning objectives were used for VMAT/3D-CRT. Parameters assessed included dose to PTV and organs-at-risk (OAR), monitor units, and multiple conformity and homogeneity indices. Plans were delivered to a phantom for time comparison. Results: Lung V 20/12.5/10/5 were less with VMAT (relative reduction 4.5%, p = .02; 3.2%, p = .01; 2.6%, p = .01; 4.2%, p = .03, respectively). Mean/maximum-doses to PTV, dose to additional OARs, 95% isodose line conformity, and target volume homogeneity were equivalent. VMAT improved conformity at both the 80% (1.87 vs. 1.93, p = .08) and 50% isodose lines (5.19 vs. 5.65, p = .01). Treatment times were reduced significantly with VMAT (mean 6.1 vs. 11.9 min, p < .01). Conclusions: Single arc VMAT planning achieves highly conformal dose distributions while controlling dose to critical structures, including significant reduction in lung dose volume parameters. Employing a VMAT technique decreases treatment times by 37-63%, reducing the chance of error introduced by intrafraction variation. The quality and efficiency of VMAT is ideally suited for stereotactic lung radiotherapy delivery.

Rapid arc - clinical rationale and results

International Nuclear Information System (INIS)

Cozzi, Lucca

2008-01-01

The presentation will focus on the background of Intensity modulation volumetric arc therapy Rapid Arc from Varian Medical Systems aiming to highlight the technical and clinical rational also from an historical perspective to the founding pillars of fast delivery with a minimum number of arcs and a minimum number of monitor units

Recent advances in vacuum arc ion sources

International Nuclear Information System (INIS)

Brown, I.G.; Anders, A.; Anders, S.; Dickinson, M.R.; MacGill, R.A.; Oks, E.M.

1995-07-01

Intense beams of metal ions can be formed from a vacuum arc ion source. Broadbeam extraction is convenient, and the time-averaged ion beam current delivered downstream can readily be in the tens of milliamperes range. The vacuum arc ion source has for these reasons found good application for metallurgical surface modification--it provides relatively simple and inexpensive access to high dose metal ion implantation. Several important source developments have been demonstrated recently, including very broad beam operation, macroparticle removal, charge state enhancement, and formation of gaseous beams. The authors have made a very broad beam source embodiment with beam formation electrodes 50 cm in diameter, producing a beam of width ∼35 cm for a nominal beam area of ∼1,000 cm 2 , and a pulsed Ti beam current of about 7 A was formed at a mean ion energy of ∼100 keV. Separately, they've developed high efficiency macroparticle-removing magnetic filters and incorporated such a filter into a vacuum arc ion source so as to form macroparticle-free ion beams. Jointly with researchers at the High Current Electronics Institute at Tomsk, Russia, and the Gesellschaft fuer Schwerionenforschung at Darmstadt, Germany, they've developed a compact technique for increasing the charge states of ions produced in the vacuum arc plasma and thus providing a simple means of increasing the ion energy at fixed extractor voltage. Finally, operation with mixed metal and gaseous ion species has been demonstrated. Here, they briefly review the operation of vacuum marc ion sources and the typical beam and implantation parameters that can be obtained, and describe these source advances and their bearing on metal ion implantation applications

Improving fiber-optic laser beam delivery by incorporating GRADIUM optics

International Nuclear Information System (INIS)

Hunter, B.V.; Leong, K.H.

1997-01-01

The performance of a fiber-optic laser beam delivery system strongly depends on the fiber and the optics used to image the fiber face on the workpiece. We have compared off-the-shelf homogenous (BK7) and GRADIUM (axial-gradient) singlets to determine what improvement the GRADIUM offers in practice to the typical laser user. The realized benefit for this application, although significant, is much smaller than would be realized by a conventional imaging application. The figure of merit for laser-based materials processing is the 86% energy-enclosure radius, which is not directly supported by commerical ray-tracing software. Therefore empirical rules of thumb are presented to understand when GRADIUM (or any other well-corrected optics) will yield meaningful improvement to the beam delivery system. copyright 1997 Optical Society of America

Proton Arc Reduces Range Uncertainty Effects and Improves Conformality Compared With Photon Volumetric Modulated Arc Therapy in Stereotactic Body Radiation Therapy for Non-Small Cell Lung Cancer

Energy Technology Data Exchange (ETDEWEB)

Seco, Joao, E-mail: jseco@partners.org [Francis H. Burr Proton Therapy Center, Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts (United States); Gu, Guan; Marcelos, Tiago; Kooy, Hanne; Willers, Henning [Francis H. Burr Proton Therapy Center, Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts (United States)

2013-09-01

Purpose: To describe, in a setting of non-small cell lung cancer (NSCLC), the theoretical dosimetric advantages of proton arc stereotactic body radiation therapy (SBRT) in which the beam penumbra of a rotating beam is used to reduce the impact of range uncertainties. Methods and Materials: Thirteen patients with early-stage NSCLC treated with proton SBRT underwent repeat planning with photon volumetric modulated arc therapy (Photon-VMAT) and an in-house-developed arc planning approach for both proton passive scattering (Passive-Arc) and intensity modulated proton therapy (IMPT-Arc). An arc was mimicked with a series of beams placed at 10° increments. Tumor and organ at risk doses were compared in the context of high- and low-dose regions, represented by volumes receiving >50% and <50% of the prescription dose, respectively. Results: In the high-dose region, conformality index values are 2.56, 1.91, 1.31, and 1.74, and homogeneity index values are 1.29, 1.22, 1.52, and 1.18, respectively, for 3 proton passive scattered beams, Passive-Arc, IMPT-Arc, and Photon-VMAT. Therefore, proton arc leads to a 30% reduction in the 95% isodose line volume to 3-beam proton plan, sparing surrounding organs, such as lung and chest wall. For chest wall, V30 is reduced from 21 cm{sup 3} (3 proton beams) to 11.5 cm{sup 3}, 12.9 cm{sup 3}, and 8.63 cm{sup 3} (P=.005) for Passive-Arc, IMPT-Arc, and Photon-VMAT, respectively. In the low-dose region, the mean lung dose and V20 of the ipsilateral lung are 5.01 Gy(relative biological effectiveness [RBE]), 4.38 Gy(RBE), 4.91 Gy(RBE), and 5.99 Gy(RBE) and 9.5%, 7.5%, 9.0%, and 10.0%, respectively, for 3-beam, Passive-Arc, IMPT-Arc, and Photon-VMAT, respectively. Conclusions: Stereotactic body radiation therapy with proton arc and Photon-VMAT generate significantly more conformal high-dose volumes than standard proton SBRT, without loss of coverage of the tumor and with significant sparing of nearby organs, such as chest wall. In addition

SU-E-T-621: Planning Methodologies for Cancer of the Anal Canal: Comparing IMRT, Rapid Arc, and Pencil Beam Scanning Proton Beam

International Nuclear Information System (INIS)

McGlade, J; Kassaee, A

2015-01-01

Purpose: To evaluate planning methods for anal canal cancer and compare the results of 9-field Intensity Modulated Radiotherapy (IMRT), Volumetric Modulated Arc Therapy (Varian, RapidArc), and Proton Pencil Beam Scanning (PBS). Methods: We generated plans with IMRT, RapidArc (RA) and PBS for twenty patients for both initial phase including nodes and cone down phase of treatment using Eclipe (Varian). We evaluated the advantage of each technique for each phase. RA plans used 2 to 4 arcs and various collimator orientations. PBS used two posterior oblique fields. We evaluated the plans comparing dose volume histogram (DVH), locations of hot spots, and PTV dose conformity. Results: Due to complex shape of target, for RA plans, multiple arcs (>2) are required to achieve optimal PTV conformity. When the PTV exceeds 15 cm in the superior-inferior direction, limitations of deliverability start to dominate. The PTV should be divided into a superior and an inferior structure. The optimization is performed with fixed jaws for each structure and collimator set to 90 degrees for the inferior PTV. Proton PBS plans show little advantage in small bowel sparing when treating the nodes. However, PBS plan reduces volumetric dose to the bladder at the cost of higher doses to the perineal skin. IMRT plans provide good target conformity, but they generate hot spots outside of the target volume. Conclusion: When using one planning technique for entire course of treatment, Multiple arc (>2) RA plans are better as compared to IMRT and PBS plans. When combining techniques, RA for the initial phase in combination with PBS for the cone down phase results in the most optimal plans

SU-E-T-621: Planning Methodologies for Cancer of the Anal Canal: Comparing IMRT, Rapid Arc, and Pencil Beam Scanning Proton Beam

Energy Technology Data Exchange (ETDEWEB)

McGlade, J; Kassaee, A [University of Pennsylvenia, Philadelphia, PA (United States)

2015-06-15

Purpose: To evaluate planning methods for anal canal cancer and compare the results of 9-field Intensity Modulated Radiotherapy (IMRT), Volumetric Modulated Arc Therapy (Varian, RapidArc), and Proton Pencil Beam Scanning (PBS). Methods: We generated plans with IMRT, RapidArc (RA) and PBS for twenty patients for both initial phase including nodes and cone down phase of treatment using Eclipe (Varian). We evaluated the advantage of each technique for each phase. RA plans used 2 to 4 arcs and various collimator orientations. PBS used two posterior oblique fields. We evaluated the plans comparing dose volume histogram (DVH), locations of hot spots, and PTV dose conformity. Results: Due to complex shape of target, for RA plans, multiple arcs (>2) are required to achieve optimal PTV conformity. When the PTV exceeds 15 cm in the superior-inferior direction, limitations of deliverability start to dominate. The PTV should be divided into a superior and an inferior structure. The optimization is performed with fixed jaws for each structure and collimator set to 90 degrees for the inferior PTV. Proton PBS plans show little advantage in small bowel sparing when treating the nodes. However, PBS plan reduces volumetric dose to the bladder at the cost of higher doses to the perineal skin. IMRT plans provide good target conformity, but they generate hot spots outside of the target volume. Conclusion: When using one planning technique for entire course of treatment, Multiple arc (>2) RA plans are better as compared to IMRT and PBS plans. When combining techniques, RA for the initial phase in combination with PBS for the cone down phase results in the most optimal plans.

Compact compressive arc and beam switchyard for energy recovery linac-driven ultraviolet free electron lasers

Science.gov (United States)

Akkermans, J. A. G.; Di Mitri, S.; Douglas, D.; Setija, I. D.

2017-08-01

High gain free electron lasers (FELs) driven by high repetition rate recirculating accelerators have received considerable attention in the scientific and industrial communities in recent years. Cost-performance optimization of such facilities encourages limiting machine size and complexity, and a compact machine can be realized by combining bending and bunch length compression during the last stage of recirculation, just before lasing. The impact of coherent synchrotron radiation (CSR) on electron beam quality during compression can, however, limit FEL output power. When methods to counteract CSR are implemented, appropriate beam diagnostics become critical to ensure that the target beam parameters are met before lasing, as well as to guarantee reliable, predictable performance and rapid machine setup and recovery. This article describes a beam line for bunch compression and recirculation, and beam switchyard accessing a diagnostic line for EUV lasing at 1 GeV beam energy. The footprint is modest, with 12 m compressive arc diameter and ˜20 m diagnostic line length. The design limits beam quality degradation due to CSR both in the compressor and in the switchyard. Advantages and drawbacks of two switchyard lines providing, respectively, off-line and on-line measurements are discussed. The entire design is scalable to different beam energies and charges.

Performance requirements of the MedAustron beam delivery system

CERN Document Server

AUTHOR|(CDS)2073034

The Austrian hadron therapy center MedAustron is currently under construction with patient treatment planned to commence in 2015. Tumors will be irradiated using proton and carbon ions, for which the steeply rising Bragg curve and finite range offer a better conformity of the dose to the geometrical shape of the tumor compared to conventional photon irradiation. The current trend is to move from passive scattering toward active scanning using a narrow pencil beam in order to reach an even better dose conformation and limit the need of patient specific hardware. The quality of the deposited dose will ultimately depend on the performance of the beam delivery chain: beam profile and extraction stability of the extracted beam, accuracy and ramp rate of the scanning magnet power supplies, and precision of the beam monitors used for verifying the delivered dose. With a sharp lateral penumbra, the transverse dose fall-off can be minimized. This is of particular importance in situations where the lesion is adjace...

Grain Refinement of Freeform Fabricated Ti-6Al-4V Alloy Using Beam/Arc Modulation

Science.gov (United States)

Mitzner, Scott; Liu, Stephen; Domack, Marcia S.; Hafley, Robert A.

2012-01-01

Grain refinement can significantly improve the mechanical properties of freeform-fabricated Ti-6Al-4V alloy, promoting increased strength and enhanced isotropy compared with coarser grained material. Large beta-grains can lead to a segregated microstructure, in regard to both alpha-phase morphology and alpha-lath orientation. Beam modulation, which has been used in conventional fusion welding to promote grain refinement, is explored in this study for use in additive manufacturing processes including electron beam freeform fabrication (EBF(sup 3)) and gas-tungsten arc (GTA) deposition to alter solidification behavior and produce a refined microstructure. The dynamic molten pool size induced by beam modulation causes rapid heat flow variance and results in a more competitive grain growth environment, reducing grain size. Consequently, improved isotropy and strength can be achieved with relatively small adjustments to deposition parameters.

Online dose reconstruction for tracked volumetric arc therapy: Real-time implementation and offline quality assurance for prostate SBRT.

Science.gov (United States)

Kamerling, Cornelis Ph; Fast, Martin F; Ziegenhein, Peter; Menten, Martin J; Nill, Simeon; Oelfke, Uwe

2017-11-01

Firstly, this study provides a real-time implementation of online dose reconstruction for tracked volumetric arc therapy (VMAT). Secondly, this study describes a novel offline quality assurance tool, based on commercial dose calculation algorithms. Online dose reconstruction for VMAT is a computationally challenging task in terms of computer memory usage and calculation speed. To potentially reduce the amount of memory used, we analyzed the impact of beam angle sampling for dose calculation on the accuracy of the dose distribution. To establish the performance of the method, we planned two single-arc VMAT prostate stereotactic body radiation therapy cases for delivery with dynamic MLC tracking. For quality assurance of our online dose reconstruction method we have also developed a stand-alone offline dose reconstruction tool, which utilizes the RayStation treatment planning system to calculate dose. For the online reconstructed dose distributions of the tracked deliveries, we could establish strong resemblance for 72 and 36 beam co-planar equidistant beam samples with less than 1.2% deviation for the assessed dose-volume indicators (clinical target volume D98 and D2, and rectum D2). We could achieve average runtimes of 28-31 ms per reported MLC aperture for both dose computation and accumulation, meeting our real-time requirement. To cross-validate the offline tool, we have compared the planned dose to the offline reconstructed dose for static deliveries and found excellent agreement (3%/3 mm global gamma passing rates of 99.8%-100%). Being able to reconstruct dose during delivery enables online quality assurance and online replanning strategies for VMAT. The offline quality assurance tool provides the means to validate novel online dose reconstruction applications using a commercial dose calculation engine. © 2017 The Authors. Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Automated analysis of images acquired with electronic portal imaging device during delivery of quality assurance plans for inversely optimized arc therapy

DEFF Research Database (Denmark)

Fredh, Anna; Korreman, Stine; Rosenschöld, Per Munck af

2010-01-01

This work presents an automated method for comprehensively analyzing EPID images acquired for quality assurance of RapidArc treatment delivery. In-house-developed software has been used for the analysis and long-term results from measurements on three linacs are presented....

Evaluation of an aSi-EPID with flattening filter free beams: Applicability to the GLAaS algorithm for portal dosimetry and first experience for pretreatment QA of RapidArc

International Nuclear Information System (INIS)

Nicolini, G.; Clivio, A.; Vanetti, E.; Cozzi, L.; Fogliata, A.; Krauss, H.; Fenoglietto, P.

2013-01-01

Purpose: To demonstrate the feasibility of portal dosimetry with an amorphous silicon mega voltage imager for flattening filter free (FFF) photon beams by means of the GLAaS methodology and to validate it for pretreatment quality assurance of volumetric modulated arc therapy (RapidArc).Methods: The GLAaS algorithm, developed for flattened beams, was applied to FFF beams of nominal energy of 6 and 10 MV generated by a Varian TrueBeam (TB). The amorphous silicon electronic portal imager [named mega voltage imager (MVI) on TB] was used to generate integrated images that were converted into matrices of absorbed dose to water. To enable GLAaS use under the increased dose-per-pulse and dose-rate conditions of the FFF beams, new operational source-detector-distance (SDD) was identified to solve detector saturation issues. Empirical corrections were defined to account for the shape of the profiles of the FFF beams to expand the original methodology of beam profile and arm backscattering correction. GLAaS for FFF beams was validated on pretreatment verification of RapidArc plans for three different TB linacs. In addition, the first pretreatment results from clinical experience on 74 arcs were reported in terms of γ analysis.Results: MVI saturates at 100 cm SDD for FFF beams but this can be avoided if images are acquired at 150 cm for all nominal dose rates of FFF beams. Rotational stability of the gantry-imager system was tested and resulted in a minimal apparent imager displacement during rotation of 0.2 ± 0.2 mm at SDD = 150 cm. The accuracy of this approach was tested with three different Varian TrueBeam linacs from different institutes. Data were stratified per energy and machine and showed no dependence with beam quality and MLC model. The results from clinical pretreatment quality assurance, provided a gamma agreement index (GAI) in the field area for six and ten FFF beams of (99.8 ± 0.3)% and (99.5 ± 0.6)% with distance to agreement and dose difference criteria

Polarimeters and energy spectrometers for the ILC beam delivery system

Energy Technology Data Exchange (ETDEWEB)

Boogert, S. [London Univ. (United Kingdom). Royal Holloway; Hildreth, M. [Univ. of Notre Dame (United States); Kaefer, K. [DESY, Hamburg (Germany); DESY, Zeuthen (DE)] (and others)

2009-02-15

This article gives an overview of current plans and issues for polarimeters and energy spectrometers in the Beam Delivery System of the ILC. It is meant to serve as a useful reference for the Detector Letter of Intent documents currently being prepared. (orig.)

A proton beam delivery system for conformal therapy and intensity modulated therapy

International Nuclear Information System (INIS)

Yu Qingchang

2001-01-01

A scattering proton beam delivery system for conformal therapy and intensity modulated therapy is described. The beam is laterally spread out by a dual-ring double scattering system and collimated by a program-controlled multileaf collimator and patient specific fixed collimators. The proton range is adjusted and modulated by a program controlled binary filter and ridge filters

Linear fixed-field multipass arcs for recirculating linear accelerators

Directory of Open Access Journals (Sweden)

V. S. Morozov

2012-06-01

Full Text Available Recirculating linear accelerators (RLA’s provide a compact and efficient way of accelerating particle beams to medium and high energies by reusing the same linac for multiple passes. In the conventional scheme, after each pass, the different energy beams coming out of the linac are separated and directed into appropriate arcs for recirculation, with each pass requiring a separate fixed-energy arc. In this paper we present a concept of an RLA return arc based on linear combined-function magnets, in which two and potentially more consecutive passes with very different energies are transported through the same string of magnets. By adjusting the dipole and quadrupole components of the constituting linear combined-function magnets, the arc is designed to be achromatic and to have zero initial and final reference orbit offsets for all transported beam energies. We demonstrate the concept by developing a design for a droplet-shaped return arc for a dogbone RLA capable of transporting two beam passes with momenta different by a factor of 2. We present the results of tracking simulations of the two passes and lay out the path to end-to-end design and simulation of a complete dogbone RLA.

Vacuum Arc Ion Sources

CERN Document Server

Brown, I.

2013-12-16

The vacuum arc ion source has evolved into a more or less standard laboratory tool for the production of high-current beams of metal ions, and is now used in a number of different embodiments at many laboratories around the world. Applications include primarily ion implantation for material surface modification research, and good performance has been obtained for the injection of high-current beams of heavy-metal ions, in particular uranium, into particle accelerators. As the use of the source has grown, so also have the operational characteristics been improved in a variety of different ways. Here we review the principles, design, and performance of vacuum arc ion sources.

Radiation Dose for Equipment in the LHC Arcs

CERN Document Server

Wittenburg, K; Spickermann, T

1998-01-01

Collisions of protons with residual gas molecules or the beam screen installed in the vacuum chamber are the main sources for the radiation dose in the LHC arcs. The dose due to proton-gas collisions depends on gas pressure, energy and intensity of the circulating beam. The dose is about equally distributed along the arc and has been calculated in previous papers. Collisions of particles with the beam screen will take place where the beam size is largest - close to focusing quadrupole magnets. For this paper the radiation doses due to particles hitting the beam screen in a quadrupole were calculated with the shower codes GEANT3.21 and FLUKA96.

IMRT delivery to a moving target by dynamic MLC tracking: delivery for targets moving in two dimensions in the beam's eye view

International Nuclear Information System (INIS)

McQuaid, D; Webb, S

2006-01-01

A new modification of the dynamic multileaf collimator (dMLC) delivery technique for intensity-modulated therapy (IMRT) is outlined. This technique enables the tracking of a target moving through rigid-body translations in a 2D trajectory in the beam's eye view. The accuracy of the delivery versus that of deliveries with no tracking and of 1D tracking techniques is quantified with clinically derived intensity-modulated beams (IMBs). Leaf trajectories calculated in the target-reference frame were iteratively synchronized assuming regular target motion. This allowed the leaves defined in the lab-reference frame to simultaneously follow the target motion and to deliver the required IMB without violation of the leaf maximum-velocity constraint. The leaves are synchronized until the gradient of the leaf position at every instant is less than a calculated maximum. The delivered fluence in the target-reference frame was calculated with a simple primary-fluence model. The new 2D tracking technique was compared with the delivered fluence produced by no-tracking deliveries and by 1D tracking deliveries for 33 clinical IMBs. For the clinical IMBs normalized to a maximum fluence of 200 MUs, the rms difference between the desired and the delivered IMB was 15.6 ± 3.3 MU for the case of a no-tracking delivery, 7.9 ± 1.6 MU for the case where only the primary component of motion was corrected and 5.1 ± 1.1 MU for the 2D tracking delivery. The residual error is due to interpolation and sampling effects. The 2D tracking delivery technique requires an increase in the delivery time evaluated as between 0 and 50% of the unsynchronized delivery time for each beam with a mean increase of 13% for the IMBs tested. The 2D tracking dMLC delivery technique allows an optimized IMB to be delivered to moving targets with increased accuracy and with acceptable increases in delivery time. When combined with real-time knowledge of the target motion at delivery time, this technique facilitates

Beam-centric algorithm for pretreatment patient position correction in external beam radiation therapy

International Nuclear Information System (INIS)

Bose, Supratik; Shukla, Himanshu; Maltz, Jonathan

2010-01-01

Purpose: In current image guided pretreatment patient position adjustment methods, image registration is used to determine alignment parameters. Since most positioning hardware lacks the full six degrees of freedom (DOF), accuracy is compromised. The authors show that such compromises are often unnecessary when one models the planned treatment beams as part of the adjustment calculation process. The authors present a flexible algorithm for determining optimal realizable adjustments for both step-and-shoot and arc delivery methods. Methods: The beam shape model is based on the polygonal intersection of each beam segment with the plane in pretreatment image volume that passes through machine isocenter perpendicular to the central axis of the beam. Under a virtual six-DOF correction, ideal positions of these polygon vertices are computed. The proposed method determines the couch, gantry, and collimator adjustments that minimize the total mismatch of all vertices over all segments with respect to their ideal positions. Using this geometric error metric as a function of the number of available DOF, the user may select the most desirable correction regime. Results: For a simulated treatment plan consisting of three equally weighted coplanar fixed beams, the authors achieve a 7% residual geometric error (with respect to the ideal correction, considered 0% error) by applying gantry rotation as well as translation and isocentric rotation of the couch. For a clinical head-and-neck intensity modulated radiotherapy plan with seven beams and five segments per beam, the corresponding error is 6%. Correction involving only couch translation (typical clinical practice) leads to a much larger 18% mismatch. Clinically significant consequences of more accurate adjustment are apparent in the dose volume histograms of target and critical structures. Conclusions: The algorithm achieves improvements in delivery accuracy using standard delivery hardware without significantly increasing

Pseudo ribbon metal ion beam source

International Nuclear Information System (INIS)

Stepanov, Igor B.; Ryabchikov, Alexander I.; Sivin, Denis O.; Verigin, Dan A.

2014-01-01

The paper describes high broad metal ion source based on dc macroparticle filtered vacuum arc plasma generation with the dc ion-beam extraction. The possibility of formation of pseudo ribbon beam of metal ions with the parameters: ion beam length 0.6 m, ion current up to 0.2 A, accelerating voltage 40 kV, and ion energy up to 160 kV has been demonstrated. The pseudo ribbon ion beam is formed from dc vacuum arc plasma. The results of investigation of the vacuum arc evaporator ion-emission properties are presented. The influence of magnetic field strength near the cathode surface on the arc spot movement and ion-emission properties of vacuum-arc discharge for different cathode materials are determined. It was shown that vacuum-arc discharge stability can be reached when the magnetic field strength ranges from 40 to 70 G on the cathode surface

Pseudo ribbon metal ion beam source.

Science.gov (United States)

Stepanov, Igor B; Ryabchikov, Alexander I; Sivin, Denis O; Verigin, Dan A

2014-02-01

The paper describes high broad metal ion source based on dc macroparticle filtered vacuum arc plasma generation with the dc ion-beam extraction. The possibility of formation of pseudo ribbon beam of metal ions with the parameters: ion beam length 0.6 m, ion current up to 0.2 A, accelerating voltage 40 kV, and ion energy up to 160 kV has been demonstrated. The pseudo ribbon ion beam is formed from dc vacuum arc plasma. The results of investigation of the vacuum arc evaporator ion-emission properties are presented. The influence of magnetic field strength near the cathode surface on the arc spot movement and ion-emission properties of vacuum-arc discharge for different cathode materials are determined. It was shown that vacuum-arc discharge stability can be reached when the magnetic field strength ranges from 40 to 70 G on the cathode surface.

The impacts of dental filling materials on RapidArc treatment planning and dose delivery: Challenges and solution

Energy Technology Data Exchange (ETDEWEB)

Mail, Noor; Al-Ghamdi, S.; Saoudi, A. [Princess Norah Oncology Center, National Guard Health Affairs, Jeddah 21423, Saudi Arabia and King Abdullah International Medical Research Center, Jeddah 21423 (Saudi Arabia); Albarakati, Y.; Ahmad Khan, M.; Saeedi, F.; Safadi, N. [Princess Norah Oncology Center, National Guard Health Affairs, Jeddah 21423 (Saudi Arabia)

2013-08-15

Purpose: The presence of high-density material in the oral cavity creates dose perturbation in both downstream and upstream directions at the surfaces of dental filling materials (DFM). In this study, the authors have investigated the effect of DFM on head and neck RapidArc treatment plans and delivery. Solutions are proposed to address (1) the issue of downstream dose perturbation, which might cause target under dosage, and (2) to reduce the upstream dose from DFM which may be the primary source of mucositis. In addition, an investigation of the clinical role of a custom-made plastic dental mold/gutter (PDM) in sparing the oral mucosa and tongue reaction is outlined.Methods: The influence of the dental filling artifacts on dose distribution was investigated using a geometrically well-defined head and neck intensity modulated radiation therapy (IMRT) verification phantom (PTW, Freiberg, Germany) with DFM inserts called amalgam, which contained 50% mercury, 25% silver, 14% tin, 8% copper, and 3% other trace metals. Three RapidArc plans were generated in the Varian Eclipse System to treat the oral cavity using the same computer tomography (CT) dataset, including (1) a raw CT image, (2) a streaking artifacts region, which was replaced with a mask of 10 HU, and (3) a 2 cm-thick 6000 HU virtual filter [a volume created in treatment planning system to compensate for beam attenuation, where the thickness of this virtual filter is based on the measured percent depth dose (PDD) data and Eclipse calculation]. The dose delivery for the three plans was verified using Gafchromic-EBT2 film measurements. The custom-made PDM technique to reduce backscatter dose was clinically tested on four head and neck cancer patients (T3, N1, M0) with DFM, two patients with PDM and the other two patients without PDM. The thickness calculation of the PDM toward the mucosa and tongue was purely based on the measured upstream dose. Patients’ with oral mucosal reaction was clinically examined

The impacts of dental filling materials on RapidArc treatment planning and dose delivery: Challenges and solution

International Nuclear Information System (INIS)

Mail, Noor; Al-Ghamdi, S.; Saoudi, A.; Albarakati, Y.; Ahmad Khan, M.; Saeedi, F.; Safadi, N.

2013-01-01

Purpose: The presence of high-density material in the oral cavity creates dose perturbation in both downstream and upstream directions at the surfaces of dental filling materials (DFM). In this study, the authors have investigated the effect of DFM on head and neck RapidArc treatment plans and delivery. Solutions are proposed to address (1) the issue of downstream dose perturbation, which might cause target under dosage, and (2) to reduce the upstream dose from DFM which may be the primary source of mucositis. In addition, an investigation of the clinical role of a custom-made plastic dental mold/gutter (PDM) in sparing the oral mucosa and tongue reaction is outlined.Methods: The influence of the dental filling artifacts on dose distribution was investigated using a geometrically well-defined head and neck intensity modulated radiation therapy (IMRT) verification phantom (PTW, Freiberg, Germany) with DFM inserts called amalgam, which contained 50% mercury, 25% silver, 14% tin, 8% copper, and 3% other trace metals. Three RapidArc plans were generated in the Varian Eclipse System to treat the oral cavity using the same computer tomography (CT) dataset, including (1) a raw CT image, (2) a streaking artifacts region, which was replaced with a mask of 10 HU, and (3) a 2 cm-thick 6000 HU virtual filter [a volume created in treatment planning system to compensate for beam attenuation, where the thickness of this virtual filter is based on the measured percent depth dose (PDD) data and Eclipse calculation]. The dose delivery for the three plans was verified using Gafchromic-EBT2 film measurements. The custom-made PDM technique to reduce backscatter dose was clinically tested on four head and neck cancer patients (T3, N1, M0) with DFM, two patients with PDM and the other two patients without PDM. The thickness calculation of the PDM toward the mucosa and tongue was purely based on the measured upstream dose. Patients’ with oral mucosal reaction was clinically examined

The number of beams in IMRT-theoretical investigations and implications for single-arc IMRT

International Nuclear Information System (INIS)

Bortfeld, Thomas

2010-01-01

The first purpose of this paper is to shed some new light on the old question of selecting the number of beams in intensity-modulated radiation therapy (IMRT). The second purpose is to illuminate the related issue of discrete static beam angles versus rotational techniques, which has recently re-surfaced due to the advancement of volumetric modulated arc therapy (VMAT). A specific objective is to find analytical expressions that allow one to address the points raised above. To make the problem mathematically tractable, it is assumed that the depth dose is flat and that the lateral dose profile can be approximated by polynomials, specifically Chebyshev polynomials of the first kind, of finite degree. The application of methods known from image reconstruction then allows one to answer the first question above as follows: the required number of beams is determined by the maximum degree of the polynomials used in the approximation of the beam profiles, which is a measure of the dose variability. There is nothing to be gained by using more beams. In realistic cases, in which the variability of the lateral dose profile is restricted in several ways, the required number of beams is of the order of 10-20. The consequence of delivering the beams with a 'leaf sweep' technique during continuous rotation of the gantry, as in VMAT, is also derived in an analytical form. The main effect is that the beams fan out, but the effect near the axis of rotation is small. This result can serve as a theoretical justification of VMAT. Overall the analytical derivations in this paper, albeit based on strong simplifications, provide new insights into, and a deeper understanding of, the beam angle problem in IMRT. The decomposition of the beam profiles into well-behaved and easily deliverable smooth functions, such as Chebyshev polynomials, could be of general interest in IMRT treatment planning.

TU-CD-304-03: Dosimetric Verification and Preliminary Comparison of Dynamic Wave Arc for SBRT Treatments

Energy Technology Data Exchange (ETDEWEB)

Burghelea, M [UZ BRUSSEL, Brussels (Belgium); BRAINLAB AG, Munich (Germany); Babes Bolyai University, Cluj-Napoca (Romania); Poels, K; Gevaert, T; Tournel, K; Dhont, J; De Ridder, M; Verellen, D [UZ BRUSSEL, Brussels (Belgium); Hung, C [BRAINLAB AG, Munich (Germany); Eriksson, K [RAYSEARCH LABORATORIES AB, Stockholm (Sweden); Simon, V [Babes Bolyai University, Cluj-Napoca (Romania)

2015-06-15

Purpose: To evaluate the potential dosimetric benefits and verify the delivery accuracy of Dynamic Wave Arc, a novel treatment delivery approach for the Vero SBRT system. Methods: Dynamic Wave Arc (DWA) combines simultaneous movement of gantry/ring with inverse planning optimization, resulting in an uninterrupted non-coplanar arc delivery technique. Thirteen SBRT complex cases previously treated with 8–10 conformal static beams (CRT) were evaluated in this study. Eight primary centrally-located NSCLC (prescription dose 4×12Gy or 8×7.5Gy) and five oligometastatic cases (2×2 lesions, 10×5Gy) were selected. DWA and coplanar VMAT plans, partially with dual arcs, were generated for each patient using identical objective functions for target volumes and OARs on the same TPS (RayStation, RaySearch Laboratories). Dosimetric differences and delivery time among these three planning schemes were evaluated. The DWA delivery accuracy was assessed using the Delta4 diode array phantom (ScandiDos AB). The gamma analysis was performed with the 3%/3mm dose and distance-to-agreement criteria. Results: The target conformity for CRT, VMAT and DWA were 0.95±0.07, 0.96±0.04 and 0.97±0.04, while the low dose spillage gradient were 5.52±1.36, 5.44±1.11, and 5.09±0.98 respectively. Overall, the bronchus, esophagus and spinal cord maximum doses were similar between VMAT and DWA, but highly reduced compared with CRT. For the lung cases, the mean dose and V20Gy were lower for the arc techniques compares with CRT, while for the liver cases, the mean dose and the V30Gy presented slightly higher values. The average delivery time of VMAT and DWA were 2.46±1.10 min and 4.25±1.67 min, VMAT presenting shorter treatment time in all cases. The DWA dosimetric verification presented an average gamma index passing rate of 95.73±1.54% (range 94.2%–99.8%). Conclusion: Our preliminary data indicated that the DWA is deliverable with clinically acceptable accuracy and has the potential to

TU-CD-304-03: Dosimetric Verification and Preliminary Comparison of Dynamic Wave Arc for SBRT Treatments

International Nuclear Information System (INIS)

Burghelea, M; Poels, K; Gevaert, T; Tournel, K; Dhont, J; De Ridder, M; Verellen, D; Hung, C; Eriksson, K; Simon, V

2015-01-01

Purpose: To evaluate the potential dosimetric benefits and verify the delivery accuracy of Dynamic Wave Arc, a novel treatment delivery approach for the Vero SBRT system. Methods: Dynamic Wave Arc (DWA) combines simultaneous movement of gantry/ring with inverse planning optimization, resulting in an uninterrupted non-coplanar arc delivery technique. Thirteen SBRT complex cases previously treated with 8–10 conformal static beams (CRT) were evaluated in this study. Eight primary centrally-located NSCLC (prescription dose 4×12Gy or 8×7.5Gy) and five oligometastatic cases (2×2 lesions, 10×5Gy) were selected. DWA and coplanar VMAT plans, partially with dual arcs, were generated for each patient using identical objective functions for target volumes and OARs on the same TPS (RayStation, RaySearch Laboratories). Dosimetric differences and delivery time among these three planning schemes were evaluated. The DWA delivery accuracy was assessed using the Delta4 diode array phantom (ScandiDos AB). The gamma analysis was performed with the 3%/3mm dose and distance-to-agreement criteria. Results: The target conformity for CRT, VMAT and DWA were 0.95±0.07, 0.96±0.04 and 0.97±0.04, while the low dose spillage gradient were 5.52±1.36, 5.44±1.11, and 5.09±0.98 respectively. Overall, the bronchus, esophagus and spinal cord maximum doses were similar between VMAT and DWA, but highly reduced compared with CRT. For the lung cases, the mean dose and V20Gy were lower for the arc techniques compares with CRT, while for the liver cases, the mean dose and the V30Gy presented slightly higher values. The average delivery time of VMAT and DWA were 2.46±1.10 min and 4.25±1.67 min, VMAT presenting shorter treatment time in all cases. The DWA dosimetric verification presented an average gamma index passing rate of 95.73±1.54% (range 94.2%–99.8%). Conclusion: Our preliminary data indicated that the DWA is deliverable with clinically acceptable accuracy and has the potential to

Capability verification of the beam delivery system in the superficially-placed tumor therapy terminal at HIRFL

International Nuclear Information System (INIS)

Dai Zhongying; Li Qiang; Xiao Guoqing; Jin Xiaodong; Yan Zheng; Chinese Academy of Sciences, Beijing

2007-01-01

The passive beam delivery system in the superficially-placed tumor therapy terminal at Heavy Ion Research Facility in Lanzhou (HIRFL), which includes two orthogonal dipole magnets as scanning system, a motor-driven energy degrader as range-shifter, series of ridge filters as range modulator and a multileaf collimator, is introduced in detail. The capacities of its important components and the whole system have been verified experimentally. The tests of the ridge filter for extending Bragg peak and the range shifter for energy adjustment show both work well. To examine the passive beam delivery system, a beam shaping experiment were carried out, simulating a three-dimensional (3D) conformal irradiation to a tumor. The encouraging experimental result confirms that 3D layer-stacking conformal irradiation can be performed by means of the passive system. The validation of the beam delivery system establishes a substantial basis for upcoming clinical trial for superficially-placed tumors with heavy ions in the therapy terminal at HIRFL. (authors)

An apparatus for sequential pulsed plasma beam treatment in combination with Arc PVD deposition

International Nuclear Information System (INIS)

Stanislawski, J.; Werner, Z.; Piekoszewski, J.; Richter, E.

2002-01-01

A hybrid type of apparatus is described which enables one to form a thin multi-layer film on the surface of any kind of solid substrate. In one process, the surface is treated with a high intensity pulse plasma beam which introduces the chosen kind of atoms into the near-surface layer of the substrate. In the second process, following the first without breaking the vacuum, the coating is formed by arc PVD (physics vapour deposition) process. Two examples of coatings formed on metallic and ceramic substrates are presented. (author)

Modeling the biophysical effects in a carbon beam delivery line by using Monte Carlo simulations

Science.gov (United States)

Cho, Ilsung; Yoo, SeungHoon; Cho, Sungho; Kim, Eun Ho; Song, Yongkeun; Shin, Jae-ik; Jung, Won-Gyun

2016-09-01

The Relative biological effectiveness (RBE) plays an important role in designing a uniform dose response for ion-beam therapy. In this study, the biological effectiveness of a carbon-ion beam delivery system was investigated using Monte Carlo simulations. A carbon-ion beam delivery line was designed for the Korea Heavy Ion Medical Accelerator (KHIMA) project. The GEANT4 simulation tool kit was used to simulate carbon-ion beam transport into media. An incident energy carbon-ion beam with energy in the range between 220 MeV/u and 290 MeV/u was chosen to generate secondary particles. The microdosimetric-kinetic (MK) model was applied to describe the RBE of 10% survival in human salivary-gland (HSG) cells. The RBE weighted dose was estimated as a function of the penetration depth in the water phantom along the incident beam's direction. A biologically photon-equivalent Spread Out Bragg Peak (SOBP) was designed using the RBE-weighted absorbed dose. Finally, the RBE of mixed beams was predicted as a function of the depth in the water phantom.

Intensity-modulated photon arc therapy for treatment of pleural mesothelioma

International Nuclear Information System (INIS)

Tobler, Matt; Watson, Gordon; Leavitt, Dennis

2002-01-01

Radiotherapy plays a key role in the definitive or adjuvant management of patients with mesothelioma of the pleural surface. Many patients are referred for radiation with intact lung following biopsy or subtotal pleurectomy. Delivery of efficacious doses of radiation to the pleural lining while avoiding lung parenchyma toxicity has been a difficult technical challenge. Using opposed photon fields produce doses in lung that result in moderate-to-severe pulmonary toxicity in 100% of patients treated. Combined photon-electron beam treatment, at total doses of 4250 cGy to the pleural surface, results in two-thirds of the lung volume receiving over 2100 cGy. We have developed a technique using intensity-modulated photon arc therapy (IMRT) that significantly improves the dose distribution to the pleural surface with concomitant decrease in dose to lung parenchyma compared to traditional techniques. IMRT treatment of the pleural lining consists of segments of photon arcs that can be intensity modulated with varying beam weights and multileaf positions to produce a more uniform distribution to the pleural surface, while at the same time reducing the overall dose to the lung itself. Computed tomography (CT) simulation is critical for precise identification of target volumes as well as critical normal structures (lung and heart). Rotational arc trajectories and individual leaf positions and weightings are then defined for each CT plane within the patient. This paper will describe the proposed rotational IMRT technique and, using simulated isodose distributions, show the improved potential for sparing of dose to the critical structures of the lung, heart, and spinal cord

On the formation of auroral arcs

International Nuclear Information System (INIS)

Stasiewicz, K.

1984-04-01

A new mechanism for auroral arc formation is presented. The characteristic linear shape of auroral arcs is determined by magnetically connected plasma clouds in the distant equatorial magnetosphere. These clouds originate as high speed plasma beams in the magnetotail and in the solar wind. It is found that the free energy for driving an auroral arc is provided by the difference of pressure between the cloud and the ambient plasma. (author)

Upgraded vacuum arc ion source for metal ion implantation

International Nuclear Information System (INIS)

Nikolaev, A. G.; Oks, E. M.; Savkin, K. P.; Yushkov, G. Yu.; Brown, I. G.

2012-01-01

Vacuum arc ion sources have been made and used by a large number of research groups around the world over the past twenty years. The first generation of vacuum arc ion sources (dubbed ''Mevva,'' for metal vapor vacuum arc) was developed at Lawrence Berkeley National Laboratory in the 1980s. This paper considers the design, performance parameters, and some applications of a new modified version of this kind of source which we have called Mevva-V.Ru. The source produces broad beams of metal ions at an extraction voltage of up to 60 kV and a time-averaged ion beam current in the milliampere range. Here, we describe the Mevva-V.Ru vacuum arc ion source that we have developed at Tomsk and summarize its beam characteristics along with some of the applications to which we have put it. We also describe the source performance using compound cathodes.

Linear Fixed-Field Multi-Pass Arcs for Recirculating Linear Accelerators

International Nuclear Information System (INIS)

Morozov, V.S.; Bogacz, S.A.; Roblin, Y.R.; Beard, K.B.

2012-01-01

Recirculating Linear Accelerators (RLA's) provide a compact and efficient way of accelerating particle beams to medium and high energies by reusing the same linac for multiple passes. In the conventional scheme, after each pass, the different energy beams coming out of the linac are separated and directed into appropriate arcs for recirculation, with each pass requiring a separate fixed-energy arc. In this paper we present a concept of an RLA return arc based on linear combined-function magnets, in which two and potentially more consecutive passes with very different energies are transported through the same string of magnets. By adjusting the dipole and quadrupole components of the constituting linear combined-function magnets, the arc is designed to be achromatic and to have zero initial and final reference orbit offsets for all transported beam energies. We demonstrate the concept by developing a design for a droplet-shaped return arc for a dog-bone RLA capable of transporting two beam passes with momenta different by a factor of two. We present the results of tracking simulations of the two passes and lay out the path to end-to-end design and simulation of a complete dog-bone RLA.

Biological-based optimization and volumetric modulated arc therapy delivery for stereotactic body radiation therapy

International Nuclear Information System (INIS)

Diot, Quentin; Kavanagh, Brian; Timmerman, Robert; Miften, Moyed

2012-01-01

Purpose: To describe biological-based optimization and Monte Carlo (MC) dose calculation-based treatment planning for volumetric modulated arc therapy (VMAT) delivery of stereotactic body radiation therapy (SBRT) in lung, liver, and prostate patients. Methods: Optimization strategies and VMAT planning parameters using a biological-based optimization MC planning system were analyzed for 24 SBRT patients. Patients received a median dose of 45 Gy [range, 34-54 Gy] for lung tumors in 1-5 fxs and a median dose of 52 Gy [range, 48-60 Gy] for liver tumors in 3-6 fxs. Prostate patients received a fractional dose of 10 Gy in 5 fxs. Biological-cost functions were used for plan optimization, and its dosimetric quality was evaluated using the conformity index (CI), the conformation number (CN), the ratio of the volume receiving 50% of the prescription dose over the planning target volume (Rx/PTV50). The quality and efficiency of the delivery were assessed according to measured quality assurance (QA) passing rates and delivery times. For each disease site, one patient was replanned using physical cost function and compared to the corresponding biological plan. Results: Median CI, CN, and Rx/PTV50 for all 24 patients were 1.13 (1.02-1.28), 0.79 (0.70-0.88), and 5.3 (3.1-10.8), respectively. The median delivery rate for all patients was 410 MU/min with a maximum possible rate of 480 MU/min (85%). Median QA passing rate was 96.7%, and it did not significantly vary with the tumor site. Conclusions: VMAT delivery of SBRT plans optimized using biological-motivated cost-functions result in highly conformal dose distributions. Plans offer shorter treatment-time benefits and provide efficient dose delivery without compromising the plan conformity for tumors in the prostate, lung, and liver, thereby improving patient comfort and clinical throughput. The short delivery times minimize the risk of patient setup and intrafraction motion errors often associated with long SBRT treatment

Dosimetric evaluation of fattening filter free photon beams

International Nuclear Information System (INIS)

Lechner, W.

2014-01-01

Very recently, conventional treatment machines able to deliver flattening filter free photon have been introduced into clinical practice. An Elekta Pricise linear accelerator LINAC which was able to deliver 6MV and 10 MV flattened (FF) and flattening filter free (FFF) photon beams was used throughout this work. The investigated modalities were 9-Field intensity modulated radiotherapy (Intensity modulated radiotherapy (IMRT)) and 360° - single arc volumetric modulated arc therapy (Volumetric modulated arc therapy (VMAT)) with flattened and unflattened photon beams. For treatment plan evaluation the concept of Pareto optimal fronts was employed. Additionally, the efficiency of these modalities was assessed. The evaluation of the treatment plan quality showed no significant difference between FF- and FFF-beams. With respect to treatment plan efficiency, a significant decrease of delivery time of IMRT treatment plans without flattening filter compared to those with filter was found. On average, the delivery time decreased by 18% and 4% for prostate and head-and-neck cases, respectively. In contrast to that, the delivery time of VMAT treatment plans without flatting filter was significantly increased by 22% and 16% for prostate and head- and-neck cases, respectively. The applicability of 14 different detectors to small field dosimetry in FF- as well as in FFF-beams was investigated by measuring output factors of 6MV and 10 MV FF- and FFF- beams. An additional MLC was attached to the treatment machine in order to generate field sizes between 0.6x0.6 cm 2 and 10x10 cm 2 . Alanine pellets were used as reference detectors for the calculation of correction factors for small field dosimetry. Compared to alanine, the solid sate detectors and the liquid filled ionization chamber generally overestimated the output factors of small fields, whereas the air filled ionzation chambers underestimated the output factors. For the shielded diodes the correction factors ranged between 8

Combined electron beam and vacuum ARC melting for barrier tube shell material

International Nuclear Information System (INIS)

Worcester, S.A.; Woods, C.R.

1989-01-01

This patent describes a process of the type wherein zirconium tetrachloride is reduced to produce a metallic zirconium sponge. The sponge is distilled to generally remove residual magnesium and magnesium chloride, and the distilled sponge is melted to produce an ingot, the improvement for making a non-crystal bar material for use in lining the interior of zirconium alloy fuel element cladding which comprises: a. forming the distilled sponge into a consumable electrode; b. melting the consumable electrode in a multiple swept beam electron furnace with a feed rate between 1 and 20 inches per hour to form an intermediate ingot; and c. vacuum arc melting the intermediate ingot to produce a homogeneous final ingot, having 50-500 ppm iron

SU-F-T-514: Evaluation of the Accuracy of Free-Breathing and Deep Inspiration Breath-Hold Gated Beam Delivery Using An Elekta Linac

International Nuclear Information System (INIS)

Jermoumi, M; Cao, D; Housley, D; Shepard, D; Xie, R

2016-01-01

Purpose: In this study, we evaluated the performance of an Elekta linac in the delivery of gated radiotherapy. We examined whether the use of either a short gating window or a long beam hold impacts the accuracy of the delivery Methods: The performance of an Elekta linac in the delivery of gated radiotherapy was assessed using a 20cmX 20cm open field with the radiation delivered using a range of beam-on and beam-off time periods. Two SBRT plans were used to examine the accuracy of gated beam delivery for clinical treatment plans. For the SBRT cases, tests were performed for both free-breathing based gating and for gated delivery with a simulated breath-hold. A MatriXX 2D ion chamber array was used for data collection, and the gating accuracy was evaluated using gamma score. Results: For the 20cmX20cm open field, the gated beam delivery agreed closely with the non-gated delivery results. Discrepancies in the agreement, however, began to appear with a 5-to-1 ratio of the beam-off to beam-on. For these tight gating windows, each beam-on segment delivered a small number of monitor units. This finding was confirmed with dose distribution analysis from the delivery of the two VMAT plans where the gamma score(±1%,2%/1mm) showed passing rates in the range of 95% to 100% for gating windows of 25%, 38%, 50%, 63%, 75%, and 83%. Using a simulated sinusoidal breathing signal with a 4 second period, the gamma score of freebreathing gating and breath-hold gating deliveries were measured in the range of 95.7% to 100%. Conclusion: The results demonstrate that Elekta linacs can be used to accurately deliver respiratory gated treatments for both free-breathing and breath-hold patients. The accuracy of beams delivered in a gated delivery mode at low small MU proved higher than similar deliveries performed in a non-gated (manually interrupted) fashion.

SU-F-T-514: Evaluation of the Accuracy of Free-Breathing and Deep Inspiration Breath-Hold Gated Beam Delivery Using An Elekta Linac

Energy Technology Data Exchange (ETDEWEB)

Jermoumi, M; Cao, D; Housley, D; Shepard, D [Department of Radiation Oncology, Swedish Cancer Institute, Seattle, WA (United States); Xie, R [Ironwood Cancer and Research Centers, Chandler, AZ (United States)

2016-06-15

Purpose: In this study, we evaluated the performance of an Elekta linac in the delivery of gated radiotherapy. We examined whether the use of either a short gating window or a long beam hold impacts the accuracy of the delivery Methods: The performance of an Elekta linac in the delivery of gated radiotherapy was assessed using a 20cmX 20cm open field with the radiation delivered using a range of beam-on and beam-off time periods. Two SBRT plans were used to examine the accuracy of gated beam delivery for clinical treatment plans. For the SBRT cases, tests were performed for both free-breathing based gating and for gated delivery with a simulated breath-hold. A MatriXX 2D ion chamber array was used for data collection, and the gating accuracy was evaluated using gamma score. Results: For the 20cmX20cm open field, the gated beam delivery agreed closely with the non-gated delivery results. Discrepancies in the agreement, however, began to appear with a 5-to-1 ratio of the beam-off to beam-on. For these tight gating windows, each beam-on segment delivered a small number of monitor units. This finding was confirmed with dose distribution analysis from the delivery of the two VMAT plans where the gamma score(±1%,2%/1mm) showed passing rates in the range of 95% to 100% for gating windows of 25%, 38%, 50%, 63%, 75%, and 83%. Using a simulated sinusoidal breathing signal with a 4 second period, the gamma score of freebreathing gating and breath-hold gating deliveries were measured in the range of 95.7% to 100%. Conclusion: The results demonstrate that Elekta linacs can be used to accurately deliver respiratory gated treatments for both free-breathing and breath-hold patients. The accuracy of beams delivered in a gated delivery mode at low small MU proved higher than similar deliveries performed in a non-gated (manually interrupted) fashion.

SU-F-T-632: On the Use of Intensity Modulated Arc Therapy for Thoracic Vertebral Metastases SBRT Treatment

Energy Technology Data Exchange (ETDEWEB)

Pokhrel, D; Mallory, M; Badkul, R; Jiang, H; Saleh, H; Wang, F; Lominska, C [University of Kansas Hospital, Kansas City, KS (United States)

2016-06-15

Purpose: To retrospectively evaluate quality, efficiency and delivery accuracy of intensity modulated arc therapy (IMAT) plans for thoracic-vertebral metastases using stereotactic body radiotherapy (SBRT). Methods: After obtaining approval of RPC-benchmark plan, seven previously treated thoracic-vertebral metastases patients with non-coplanar hybrid arcs(NC-HA)using 1–2 3D-dynamic conformal partial-arcs plus 7–9 IMRT-beams were re-optimized with IMAT using 3 full co-planar arcs. Tumors were located between T2–T7. T1/T2-weighted MRI images were co-registered with planning-CT. PTVs were between 24.3–240.1cc(median=48.1cc). Prescription was 30Gy in 5 fractions with 6-MV beams at Novalis-TX consisting of HD-MLC.Plans were compared for target coverage:conformality index(CI),homogeneity index(HI),PTVD90. Organs-at-risks(OARs)was evaluated for spinal cord(Dmax, D0.35cc, and D1.2cc), esophagus(Dmax and D5cc),heart(Dmax, D15cc)and lung(V5 and V10). Dose delivery efficiency and accuracy of each IMAT plan was assessed via quality assurance(QA) plan. Beam-on time was recorded and a gamma index was used to compare agreement between planned and measured doses. Results: SBRT IMAT plans resulted in superior CI(1.02 vs. 1.36, p=0.05) and HI (0.14 vs. 0.27, p=0.01). PTVD90 was improved but statistically insignificant (31.0 vs. 30.4Gy, p=0.38). IMAT resulted in statistically significant improvements in OARs sparing: esophagus max(22.5 vs. 27.0Gy, p=0.03), esophagus 5cc (17.6 vs. 21.5Gy, p=0.02) and heart max(13.1 vs. 15.8Gy, p=0.03). Spinal cord,lung V5 and V10 were lower but statistically insignificant. Average total MU and beam-on time were 2598±354 vs. 3542±495 and 4.7±0.6 min vs. 7.1±1.0min for IMAT vs. NC-HA (without accounting for couch kicks time for NC-HA). IMAT plans demonstrated an accurate dose delivery of 95.5±1.0% for clinical gamma passing-rate of 2%/2mm criteria on MapCHECK, that was comparable to NC-HA plans. Conclusion: IMAT plans provided highly

Silica hollow core microstructured fibers for beam delivery in industrial and medical applications

Directory of Open Access Journals (Sweden)

Jonathan Dale Shephard

2015-04-01

Full Text Available The focus of this review is our recent work to develop microstructured hollow core fibers for two applications where the flexible delivery of a single mode beam is desired. Also, a review of other fiber based solutions is included.High power, short-pulsed lasers are widely used for micro-machining, providing high precision and high quality. However, the lack of truly flexible beam delivery systems limits their application to the processing of relatively small planar components. To address this, we developed hollow-core optical fibers for the 1 μm and green wavelength ranges. The hollow core overcomes the power delivery limitations of conventional silica fibers arising from nonlinear effects and material damage in the solid core. We have characterized such fibers in terms of power handling capability, damage threshold, bend loss and dispersion, and practically demonstrated delivery of high peak power pulses from the nanosecond to the femtosecond regime. Such fibers are ideal candidates for industrial laser machining applications.In laser surgical applications, meanwhile, an Er:YAG laser (2.94 μm is frequently the laser of choice because the water contained in tissue strongly absorbs this wavelength. If this laser beam is precisely delivered damage to surrounding tissue can be minimized. A common delivery method of surgical lasers, for use in the operating theatre, is articulated arms that are bulky, cumbersome and unsuitable for endoscopic procedures. To address this need for flexible mid-IR delivery we developed silica based hollow core fibers. By minimizing the overlap of the light with glass it is possible to overcome the material absorption limits of silica and achieve low attenuation. Additionally, it is possible to deliver pulse energies suitable for the ablation of both hard and soft tissue even with very small bend radii. The flexibility and small physical size of systems based on these fibers will enable new minimally invasive surgical

Detection and correction for EPID and gantry sag during arc delivery using cine EPID imaging.

Science.gov (United States)

Rowshanfarzad, Pejman; Sabet, Mahsheed; O'Connor, Daryl J; McCowan, Peter M; McCurdy, Boyd M C; Greer, Peter B

2012-02-01

Electronic portal imaging devices (EPIDs) have been studied and used for pretreatment and in-vivo dosimetry applications for many years. The application of EPIDs for dosimetry in arc treatments requires accurate characterization of the mechanical sag of the EPID and gantry during rotation. Several studies have investigated the effects of gravity on the sag of these systems but each have limitations. In this study, an easy experiment setup and accurate algorithm have been introduced to characterize and correct for the effect of EPID and gantry sag during arc delivery. Three metallic ball bearings were used as markers in the beam: two of them fixed to the gantry head and the third positioned at the isocenter. EPID images were acquired during a 360° gantry rotation in cine imaging mode. The markers were tracked in EPID images and a robust in-house developed MATLAB code was used to analyse the images and find the EPID sag in three directions as well as the EPID + gantry sag by comparison to the reference gantry zero image. The algorithm results were then tested against independent methods. The method was applied to compare the effect in clockwise and counter clockwise gantry rotations and different source-to-detector distances (SDDs). The results were monitored for one linear accelerator over a course of 15 months and six other linear-accelerators from two treatment centers were also investigated using this method. The generalized shift patterns were derived from the data and used in an image registration algorithm to correct for the effect of the mechanical sag in the system. The Gamma evaluation (3%, 3 mm) technique was used to investigate the improvement in alignment of cine EPID images of a fixed field, by comparing both individual images and the sum of images in a series with the reference gantry zero image. The mechanical sag during gantry rotation was dependent on the gantry angle and was larger in the in-plane direction, although the patterns were not

Dynamic electron arc radiotherapy (DEAR): a feasibility study

International Nuclear Information System (INIS)

Rodrigues, Anna; Yin, Fang-Fang; Wu, Qiuwen

2014-01-01

Compared to other radiation therapy modalities, clinical electron beam therapy has remained practically unchanged for the past few decades even though electron beams with multiple energies are widely available on most linacs. In this paper, we present the concept of dynamic electron arc radiotherapy (DEAR), a new conformal electron therapy technique with synchronized couch motion. DEAR utilizes combination of gantry rotation, couch motion, and dose rate modulation to achieve desirable dose distributions in patient. The electron applicator is kept to minimize scatter and maintain narrow penumbra. The couch motion is synchronized with the gantry rotation to avoid collision between patient and the electron cone. In this study, we investigate the feasibility of DEAR delivery and demonstrate the potential of DEAR to improve dose distributions on simple cylindrical phantoms. DEAR was delivered on Varian's TrueBeam linac in Research Mode. In conjunction with the recorded trajectory log files, mechanical motion accuracies and dose rate modulation precision were analyzed. Experimental and calculated dose distributions were investigated for different energies (6 and 9 MeV) and cut-out sizes (1×10 cm 2  and 3×10 cm 2  for a 15×15 cm 2  applicator). Our findings show that DEAR delivery is feasible and has the potential to deliver radiation dose with high accuracy (root mean square error, or RMSE of <0.1 MU, <0.1° gantry, and <0.1 cm couch positions) and good dose rate precision (1.6 MU min −1 ). Dose homogeneity within ±2% in large and curved targets can be achieved while maintaining penumbra comparable to a standard electron beam on a flat surface. Further, DEAR does not require fabrication of patient-specific shields. These benefits make DEAR a promising technique for conformal radiotherapy of superficial tumors. (paper)

Presentations from the Workshop On SABER: South Arc Beam Experimental Region, March 15-16, 2006, Menlo Park, California

International Nuclear Information System (INIS)

Noble, R.

2006-01-01

SABER (the South Arc Beam Experimental Region) is a proposed facility for experiments with 30 GeV electron and positron beams from the SLAC linac. The combination of a short bunch length (s z ∼ 30 microns), high beam charge (3 nC), and small focal spot size (s r = 10 microns) will offer unique scientific opportunities. For more detailed information about the SABER facility and an overview of some of the science possible take a look at the SABER proposal. Initial experiments with electrons could start as early as 2007. A central goal of SABER is to provide a facility responsive to the research needs of its users. The workshop's purposes are to introduce SABER to the potential user community and to explore the range of experiments that are possible. This is an opportunity for the research community to provide input about science at SABER and on the required beam parameters and infrastructure

A high current metal vapour vacuum arc ion source for ion implantation studies

International Nuclear Information System (INIS)

Evans, P.J.; Noorman, J.T.; Watt, G.C.; Cohen, D.D.; Bailey, G.M.

1989-01-01

The main features of the metal vapour vacuum arc(MEVA) as an ion source are presented. The technology utilizes the plasma production capabilities of a vacuum arc cathode. Some of the ions produced in this discharge flow through the anode and the 3 extraction grids to form an extracted ion beam. The high beam current and the potential for generating broad beams, make this technology suitable for implantation of large surface areas. The composition of the vacuum arc cathode determines the particular ions obtained from the MEVA source. 3 refs., 1 tab., 2 figs

A Case Study in Proton Pencil-Beam Scanning Delivery

International Nuclear Information System (INIS)

Kooy, Hanne M.; Clasie, Benjamin M.; Lu, H.-M.; Madden, Thomas M.; Bentefour, Hassan; Depauw, Nicolas M.S.; Adams, Judy A.; Trofimov, Alexei V.; Demaret, Denis; Delaney, Thomas F.; Flanz, Jacob B.

2010-01-01

Purpose: We completed an implementation of pencil-beam scanning (PBS), a technology whereby a focused beam of protons, of variable intensity and energy, is scanned over a plane perpendicular to the beam axis and in depth. The aim of radiotherapy is to improve the target to healthy tissue dose differential. We illustrate how PBS achieves this aim in a patient with a bulky tumor. Methods and Materials: Our first deployment of PBS uses 'broad' pencil-beams ranging from 20 to 35 mm (full-width-half-maximum) over the range interval from 32 to 7 g/cm 2 . Such beam-brushes offer a unique opportunity for treating bulky tumors. We present a case study of a large (4,295 cc clinical target volume) retroperitoneal sarcoma treated to 50.4 Gy relative biological effectiveness (RBE) (presurgery) using a course of photons and protons to the clinical target volume and a course of protons to the gross target volume. Results: We describe our system and present the dosimetry for all courses and provide an interdosimetric comparison. Discussion: The use of PBS for bulky targets reduces the complexity of treatment planning and delivery compared with collimated proton fields. In addition, PBS obviates, especially for cases as presented here, the significant cost incurred in the construction of field-specific hardware. PBS offers improved dose distributions, reduced treatment time, and reduced cost of treatment.

Telerobotic system concept for real-time soft-tissue imaging during radiotherapy beam delivery.

Science.gov (United States)

Schlosser, Jeffrey; Salisbury, Kenneth; Hristov, Dimitre

2010-12-01

The curative potential of external beam radiation therapy is critically dependent on having the ability to accurately aim radiation beams at intended targets while avoiding surrounding healthy tissues. However, existing technologies are incapable of real-time, volumetric, soft-tissue imaging during radiation beam delivery, when accurate target tracking is most critical. The authors address this challenge in the development and evaluation of a novel, minimally interfering, telerobotic ultrasound (U.S.) imaging system that can be integrated with existing medical linear accelerators (LINACs) for therapy guidance. A customized human-safe robotic manipulator was designed and built to control the pressure and pitch of an abdominal U.S. transducer while avoiding LINAC gantry collisions. A haptic device was integrated to remotely control the robotic manipulator motion and U.S. image acquisition outside the LINAC room. The ability of the system to continuously maintain high quality prostate images was evaluated in volunteers over extended time periods. Treatment feasibility was assessed by comparing a clinically deployed prostate treatment plan to an alternative plan in which beam directions were restricted to sectors that did not interfere with the transabdominal U.S. transducer. To demonstrate imaging capability concurrent with delivery, robot performance and U.S. target tracking in a phantom were tested with a 15 MV radiation beam active. Remote image acquisition and maintenance of image quality with the haptic interface was successfully demonstrated over 10 min periods in representative treatment setups of volunteers. Furthermore, the robot's ability to maintain a constant probe force and desired pitch angle was unaffected by the LINAC beam. For a representative prostate patient, the dose-volume histogram (DVH) for a plan with restricted sectors remained virtually identical to the DVH of a clinically deployed plan. With reduced margins, as would be enabled by real

Telerobotic system concept for real-time soft-tissue imaging during radiotherapy beam delivery

International Nuclear Information System (INIS)

Schlosser, Jeffrey; Salisbury, Kenneth; Hristov, Dimitre

2010-01-01

Purpose: The curative potential of external beam radiation therapy is critically dependent on having the ability to accurately aim radiation beams at intended targets while avoiding surrounding healthy tissues. However, existing technologies are incapable of real-time, volumetric, soft-tissue imaging during radiation beam delivery, when accurate target tracking is most critical. The authors address this challenge in the development and evaluation of a novel, minimally interfering, telerobotic ultrasound (U.S.) imaging system that can be integrated with existing medical linear accelerators (LINACs) for therapy guidance. Methods: A customized human-safe robotic manipulator was designed and built to control the pressure and pitch of an abdominal U.S. transducer while avoiding LINAC gantry collisions. A haptic device was integrated to remotely control the robotic manipulator motion and U.S. image acquisition outside the LINAC room. The ability of the system to continuously maintain high quality prostate images was evaluated in volunteers over extended time periods. Treatment feasibility was assessed by comparing a clinically deployed prostate treatment plan to an alternative plan in which beam directions were restricted to sectors that did not interfere with the transabdominal U.S. transducer. To demonstrate imaging capability concurrent with delivery, robot performance and U.S. target tracking in a phantom were tested with a 15 MV radiation beam active. Results: Remote image acquisition and maintenance of image quality with the haptic interface was successfully demonstrated over 10 min periods in representative treatment setups of volunteers. Furthermore, the robot's ability to maintain a constant probe force and desired pitch angle was unaffected by the LINAC beam. For a representative prostate patient, the dose-volume histogram (DVH) for a plan with restricted sectors remained virtually identical to the DVH of a clinically deployed plan. With reduced margins, as

Dynamic intensity-modulated non-coplanar arc radiotherapy (INCA) for head and neck cancer

International Nuclear Information System (INIS)

Krayenbuehl, Jerome; Davis, J. Bernard; Ciernik, I. Frank

2006-01-01

Background and purpose: To define the potential advantages of intensity-modulated radiotherapy (IMRT) applied using a non-coplanar dynamic arc technique for the treatment of head and neck cancer. Materials and methods: External beam radiotherapy (EBRT) was planned in ten patients with head and neck cancer using coplanar IMRT and non-coplanar arc techniques, termed intensity modulated non-coplanar arc EBRT (INCA). Planning target volumes (PTV1) of first order covered the gross tumor volume and surrounding clinical target volume treated with 68-70 Gy, whereas PTV2 covered the elective lymph nodes with 54-55 Gy using a simultaneous internal boost. Treatment plan comparison between IMRT and INCA was carried out using dose-volume histogram and 'equivalent uniform dose' (EUD). Results: INCA resulted in better dose coverage and homogeneity of the PTV1, PTV2, and reduced dose delivered to most of the organs at risk (OAR). For the parotid glands, a reduction of the mean dose of 2.9 (±2.0) Gy was observed (p 0.002), the mean dose to the larynx was reduced by 6.9 (±2.9) Gy (p 0.003), the oral mucosa by 2.4 (±1.1) Gy (p < 0.001), and the maximal dose to the spinal cord by 3.2 (±1.7) Gy (p = 0.004). The mean dose to the brain was increased by 3.0 (±1.4) Gy (p = 0.002) and the mean lung dose increased by 0.2 (±0.4) Gy (p = 0.87). The EUD suggested better avoidance of the OAR, except for the lung, and better coverage and dose uniformity were achieved with INCA compared to IMRT. Conclusion: Dose delivery accuracy with IMRT using a non-coplanar dynamic arc beam geometry potentially improves treatment of head and neck cancer

Beam delivery system tuning and luminosity monitoring in the Compact Linear Collider

Directory of Open Access Journals (Sweden)

B. Dalena

2012-05-01

Full Text Available Emittance preservation in the beam delivery system (BDS is one of the major challenges in the Compact Linear Collider (CLIC. The fast detuning of the final focus optics requires an on-line tuning procedure in order to keep luminosity close to the maximum. In this paper we discuss different tuning techniques to mitigate the displacement of magnets in the CLIC BDS and in particular in the final focus system. Some of them require a fast luminosity measurement. Here we study the possibility to use beam-beam background processes at CLIC 3 TeV c.m. energy as a fast luminosity signal. In particular, the hadron multiplicity in the detector region is investigated.

Volumetric modulated arc radiotherapy for esophageal cancer

International Nuclear Information System (INIS)

Vivekanandan, Nagarajan; Sriram, Padmanaban; Syam Kumar, S.A.; Bhuvaneswari, Narayanan; Saranya, Kamalakannan

2012-01-01

A treatment planning study was performed to evaluate the performance of volumetric arc modulation with RapidArc (RA) against 3D conformal radiation therapy (3D-CRT) and conventional intensity-modulated radiation therapy (IMRT) techniques for esophageal cancer. Computed tomgraphy scans of 10 patients were included in the study. 3D-CRT, 4-field IMRT, and single-arc and double-arc RA plans were generated with the aim to spare organs at risk (OAR) and healthy tissue while enforcing highly conformal target coverage. The planning objective was to deliver 54 Gy to the planning target volume (PTV) in 30 fractions. Plans were evaluated based on target conformity and dose-volume histograms of organs at risk (lung, spinal cord, and heart). The monitor unit (MU) and treatment delivery time were also evaluated to measure the treatment efficiency. The IMRT plan improves target conformity and spares OAR when compared with 3D-CRT. Target conformity improved with RA plans compared with IMRT. The mean lung dose was similar in all techniques. However, RA plans showed a reduction in the volume of the lung irradiated at V 20Gy and V 30Gy dose levels (range, 4.62–17.98%) compared with IMRT plans. The mean dose and D 35% of heart for the RA plans were better than the IMRT by 0.5–5.8%. Mean V 10Gy and integral dose to healthy tissue were almost similar in all techniques. But RA plans resulted in a reduced low-level dose bath (15–20 Gy) in the range of 14–16% compared with IMRT plans. The average MU needed to deliver the prescribed dose by RA technique was reduced by 20–25% compared with IMRT technique. The preliminary study on RA for esophageal cancers showed improvements in sparing OAR and healthy tissue with reduced beam-on time, whereas only double-arc RA offered improved target coverage compared with IMRT and 3D-CRT plans.

Scintillation screen applications in a vacuum arc ion source with composite hydride cathode

Science.gov (United States)

Wang, X. H.; Tuo, X. G.; Yang, Z.; Peng, Y. F.; Li, J.; Lv, H. Y.; Li, J. H.; Long, J. D.

2018-05-01

Vacuum arc ion source with composite hydride cathode was developed to produce intense ion beams which can be applied in particle accelerator injections. Beam profile and beam composition are two fundamental parameters of the beam for the vacuum arc ion source in such specific applications. An aluminum-coated scintillation screen with an ICCD camera readout was used to show the space-time distribution of the beam directly. A simple magnetic analysis assembly with the scintillation screen shows the beam composition information of this kind ion source. Some physical and technical issues are discussed and analyzed in the text.

SU-F-T-279: Impact of Beam Energy Drifts On IMRT Delivery Accuracy

International Nuclear Information System (INIS)

Goddu, S; Kamal, G; Herman, A; Edwards, S; Cai, B; Yaddanapudi, S; Oddiraju, S; Rangaraj, D; Mutic, S

2016-01-01

Purpose: According to TG-40 percent-depth-dose (PDD) tolerance is ±2% but TG-142 is ±1%. Now the question is, which one is relevant in IMRT era? The primary objective of this study is to evaluate dosimetric impact of beam-energy-drifts on IMRT-delivery. Methods: Beam-energy drifts were simulated by adjusting Linac’s bending-magnet-current (BMC) followed by tuning the pulse-forming network and adjusting gun-current. PDD change of −0.6% and +1.2% were tested. Planar-dosimetry measurements were performed using an ionization-chamber-array in solid-water phantoms. Study includes 10-head-and-neck and 3-breast cancer patients. en-face beam-deliveries were also tested at 1.3cm and 5.3cm depths. Composite and single-field dose-distributions were compared against the plans to determine %Gamma pass-rates (%GPRs). For plan dose comparisons, changes in %Gamma pass-rates (cPGPRs) were computed/reported to exclude the differences between dose-computation and delivery. Dose distributions of the drifted-energies were compared against their baseline measurements to determine the% GPRs. A Gamma criteria of 3%/3mm was considered for plan-dose comparisons while 3%/1mm used for measured dose intercomparisons. Results: For composite-dose delivery, average cPGPRs were 0.41%±2.48% and −2.54%±3.65% for low-energy (LE) and high-energy (HE) drifts, respectively. For measured dose inter-comparisons, the average%GPRs were 98.4%±2.2% (LE-drift) and 95.8%±4.0 (HE-drift). The average %GPR of 92.6%±4.3% was noted for the worst-case scenario comparing LE-drift to HE-drift. All en-face beams at 5.3 cm depth have cPGPRs within ±4% of the baseline-energy measurements. However, greater variations were noted for 1.3cm depth. Average %GPRs for drifted energies were >99% at 5.3cm and >97% at 1.3cm depths. However, for the worst-case scenario (LE-drift to HE-drift) these numbers dropped to 95.2% at 5.3cm and 93.1% at 1.3cm depths. Conclusion: The dosimetric impact of beam-energy drifts was

Single-Arc IMRT?

International Nuclear Information System (INIS)

Bortfeld, Thomas; Webb, Steve

2009-01-01

The idea of delivering intensity-modulated radiation therapy (IMRT) with a multileaf collimator in a continuous dynamic mode during a single rotation of the gantry has recently gained momentum both in research and industry. In this note we investigate the potential of this Single-Arc IMRT technique at a conceptual level. We consider the original theoretical example case from Brahme et al that got the field of IMRT started. Using analytical methods, we derive deliverable intensity 'landscapes' for Single-Arc as well as standard IMRT and Tomotherapy. We find that Tomotherapy provides the greatest flexibility in shaping intensity landscapes and that it allows one to deliver IMRT in a way that comes close to the ideal case in the transverse plane. Single-Arc and standard IMRT make compromises in different areas. Only in relatively simple cases that do not require substantial intensity modulation will Single-Arc be dosimetrically comparable to Tomotherapy. Compared with standard IMRT, Single-Arc could be dosimetrically superior in certain cases if one is willing to accept the spreading of low dose values over large volumes of normal tissue. In terms of treatment planning, Single-Arc poses a more challenging optimization problem than Tomotherapy or standard IMRT. We conclude that Single-Arc holds potential as an efficient IMRT technique especially for relatively simple cases. In very complex cases, Single-Arc may unduly compromise the quality of the dose distribution, if one tries to keep the treatment time below 2 min or so. As with all IMRT techniques, it is important to explore the tradeoff between plan quality and the efficiency of its delivery carefully for each individual case. (note)

SU-F-T-529: Dosimetric Investigation of a Rotating Gamma Ray System for ImagedGuided Modulated Arc Radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Ma, C; Chibani, O; Eldib, A; Chen, L [Fox Chase Cancer Center, Philadelphia, PA (United States); Li, J [Cyber Medical Inc, Xian (China)

2016-06-15

Purpose: Because of their effectiveness and efficiency, rotational arc radiotherapy (MAT) techniques have been developed on both specialty machines such as Tomotherapy and conventional linear accelerators. This work investigates a new rotating Gamma therapy system for image guided MAT and SBRT of intra/extracranial tumors. Methods: The CyberMAT system (Cyber Medical Corp., China) consists of a ring gantry with a gamma source (effective source size 1cm and 1.7cm respectively), a 120-leaf MLC, a kV CBCT and an EPID. The treatment couch provides 6-degrees-of-freedom motion compensation and the kV CBCT system has a spatial resolution of 0.4mm for target localization. The maximum dose rate is >4.0 Gy/min and the maximum field size is 40cm × 40cm. Monte Carlo simulations were used to compute dose distributions and compare with measurements. A retrospective study of 125 previously treated SBRT patients was performed to evaluate the dosimetric characteristics of CyberMAT in comparison with existing VMAT systems. Results: Monte Carlo results confirmed the CyberMAT design parameters including output factors and 3D dose distributions. Its beam penumbra is 5mm to 10mm for field sizes 1cm to 10cm, respectively and its isocenter accuracy is <0.5mm. Compared to the 6 MV photons of Tomotherapy and conventional linacs, Cobalt beams produce lower-energy secondary electrons that exhibit better dose properties in low-density lung tissues. Cobalt beams are ideal for peripheral lung tumors with half-arc arrangements to spare the opposite lung and other critical structures. Superior dose distributions have been obtained for brain, head and neck, breast, spine and lung tumors with half/full arc arrangements. Conclusion: Because of the unique dosimetric properties of Cobalt sources and its accurate stereotaxy/dose delivery CyberMAT is ideally suited for image guided MAT and SBRT. Full-arc arrangements are superior for brain and H&N treatments while half-arc arrangements produce best dose

SU-E-T-248: Near Real-Time Analysis of Radiation Delivery and Imaging, Accuracy to Ensure Patient Safety

Energy Technology Data Exchange (ETDEWEB)

Wijesooriya, K; Seitter, K; Desai, V; Read, P; Larner, J [University of Virginia Health Systems, Charlottesville, VA (United States)

2014-06-01

Purpose: To develop and optimize an effective software method for comparing planned to delivered control point machine parameters for all VARIAN TrueBeam treatments so as to permit (1) assessment of a large patient pool throughout their treatment course to quantify treatment technique specific systematic and random uncertainty of observables, (2) quantify the site specific daily imaging shifts required for target alignment, and (3) define tolerance levels for mechanical parameters and imaging parameters based on statistical analysis data gathered, and the dosimetric impact of variations. Methods: Treatment and imaging log files were directly compared to plan parameters for Eclipse and Pinnacle planned treatments via 3D, IMRT, control point, RapidArc, and electrons. Each control point from all beams/arcs (7984) for all fractions (1940) of all patients treated over six months were analyzed. At each control point gantry angle, collimator angle, couch angle, jaw positions, MLC positions, MU were compared. Additionally per-treatment isocenter shifts were calculated. Results were analyzed as a whole in treatment type subsets: IMRT, 3D, RapidArc; and in treatment site subsets: brain, chest/mediastinum, esophagus, H and N, lung, pelvis, prostate. Results: Daily imaging isocenter shifts from initial external tattoo alignment were dependent on the treatment site with < 0.5 cm translational shifts for H and N, Brain, and lung SBRT, while pelvis, esophagus shifts were ∼1 cm. Mechanical delivery parameters were within tolerance levels for all sub-beams. The largest variations were for RapidArc plans: gantry angle 0.11±0.12,collimator angle 0.00±0.00, jaw positions 0.48±0.26, MLC leaf positions 0.66±0.08, MU 0.14±0.34. Conclusion: Per-control point validation reveals deviations between planned and delivered parameters. If used in a near real-time error checking system, patient safety can be improved by equipping the treatment delivery system with additional forcing

SU-E-T-248: Near Real-Time Analysis of Radiation Delivery and Imaging, Accuracy to Ensure Patient Safety

International Nuclear Information System (INIS)

Wijesooriya, K; Seitter, K; Desai, V; Read, P; Larner, J

2014-01-01

Purpose: To develop and optimize an effective software method for comparing planned to delivered control point machine parameters for all VARIAN TrueBeam treatments so as to permit (1) assessment of a large patient pool throughout their treatment course to quantify treatment technique specific systematic and random uncertainty of observables, (2) quantify the site specific daily imaging shifts required for target alignment, and (3) define tolerance levels for mechanical parameters and imaging parameters based on statistical analysis data gathered, and the dosimetric impact of variations. Methods: Treatment and imaging log files were directly compared to plan parameters for Eclipse and Pinnacle planned treatments via 3D, IMRT, control point, RapidArc, and electrons. Each control point from all beams/arcs (7984) for all fractions (1940) of all patients treated over six months were analyzed. At each control point gantry angle, collimator angle, couch angle, jaw positions, MLC positions, MU were compared. Additionally per-treatment isocenter shifts were calculated. Results were analyzed as a whole in treatment type subsets: IMRT, 3D, RapidArc; and in treatment site subsets: brain, chest/mediastinum, esophagus, H and N, lung, pelvis, prostate. Results: Daily imaging isocenter shifts from initial external tattoo alignment were dependent on the treatment site with < 0.5 cm translational shifts for H and N, Brain, and lung SBRT, while pelvis, esophagus shifts were ∼1 cm. Mechanical delivery parameters were within tolerance levels for all sub-beams. The largest variations were for RapidArc plans: gantry angle 0.11±0.12,collimator angle 0.00±0.00, jaw positions 0.48±0.26, MLC leaf positions 0.66±0.08, MU 0.14±0.34. Conclusion: Per-control point validation reveals deviations between planned and delivered parameters. If used in a near real-time error checking system, patient safety can be improved by equipping the treatment delivery system with additional forcing

SU-E-J-53: Dosimetric Evaluation at Volumetric Modulated Arc Therapy for Treatment of Prostate Cancer Using Single Or Double Arcs

Energy Technology Data Exchange (ETDEWEB)

Silva, D; Salmon, H; Pavan, G; Nardi, S; Anderson, E; Fairbanks, L; Junior, J; Cursino, F; Colodette, K [GRUPO COI, Rio De Janeiro, Rio De Janeiro (Brazil)

2014-06-01

Purpose: Evaluate and compare retrospective prostate treatment plan using Volumetric Modulated Arc Therapy (RapidArc™ - Varian) technique with single or double arcs at COI Group. Methods: Ten patients with present prostate and seminal vesicle neoplasia were replanned as a target treatment volume and a prescribed dose of 78 Gy. A baseline planning, using single arc, was developed for each case reaching for the best result on PTV, in order to minimize the dose on organs at risk (OAR). Maintaining the same optimization objectives used on baseline plan, two copies for optimizing single and double arcs, have been developed. The plans were performed with 10 MV photon beam energy on Eclipse software, version 11.0, making use of Trilogy linear accelerator with Millenium HD120 multileaf collimator. Comparisons on PTV have been performed, such as: maximum, minimum and mean dose, gradient dose, as well as the quantity of monitor units, treatment time and homogeneity and conformity index. OARs constrains dose have been evaluated, comparing both optimizations. Results: Regarding PTV coverage, the difference of the minimum, maximum and mean dose were 1.28%, 0.7% and 0.2% respectively higher for single arc. When analyzed the index of homogeneity found a difference of 0.99% higher when compared with double arcs. However homogeneity index was 0.97% lower on average by using single arc. The doses on the OARs, in both cases, were in compliance to the recommended limits RTOG 0415. With the use of single arc, the quantity of monitor units was 10,1% lower, as well as the Beam-On time, 41,78%, when comparing double arcs, respectively. Conclusion: Concerning the optimization of patients with present prostate and seminal vesicle neoplasia, the use of single arc reaches similar objectives, when compared to double arcs, in order to decrease the treatment time and the quantity of monitor units.

SU-F-T-338: Flattening Filter Free Photon Beams Can Achieve the Same Plan Quality as Conventional Flattened Beams for Prostate Radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Kolar, M; Szwedowski, R; Greskovich, J; Xia, P [Cleveland Clinic, Cleveland, OH (United States)

2016-06-15

Purpose: Some modern linear accelerators are equipped with one low energy flat beam and two flattening filter free (FFF) beams at high and low energies. The purpose of this study is to investigate whether the high energy FFF beam can produce the same plan quality as the conventional low energy flat beam, using a volumetric modulated arc (VMAT) technique for prostate patients. Methods: Ten prostate cancer patients were selected with a prescription of 78Gy. For each patient, three plans were created: (a) double arc flat 6MV plan used clinically; (b) double arc 10MV FFF plan; (c) single arc 10MV FFF plan. Each plan was prescribed so that at least 95% of the PTV received the prescription dose. The following dosimetric endpoints were evaluated: volume receiving 78Gy (V78) of the CTV and PTV, PTV conformality index (CI, ratio of prescription isodose volume to the PTV volume), bladder volume receiving 70Gy (V70) and 60Gy (V60), rectum volume receiving 70Gy (V70) and 50Gy (V50), dose to 10cc of the rectum, and volume of both femoral heads receiving 50Gy (V50). Total monitor units for each plan were recorded. Results: No significant difference was found for all dosimetric endpoints between all plans (p>0.05). Compared to the 6MV plans, monitor units were higher with the double arc 10MV FFF plans and lower with the single arc 10MV FFF plans, 29% and 4% respectively. Conclusion: Both single arc and double arc 10MV FFF VMAT can achieve equivalent plan quality as 6MV flat beam double arc treatment plans. With the gantry speed restriction, a high dose rate of 2400MU/min may allow the optimizer to use more MUs than actually needed. Single arc 10MV FFF VMAT plans are a reasonable alternative to double arc 6MV flat beam VMAT plans.

SU-F-T-338: Flattening Filter Free Photon Beams Can Achieve the Same Plan Quality as Conventional Flattened Beams for Prostate Radiotherapy

International Nuclear Information System (INIS)

Kolar, M; Szwedowski, R; Greskovich, J; Xia, P

2016-01-01

Purpose: Some modern linear accelerators are equipped with one low energy flat beam and two flattening filter free (FFF) beams at high and low energies. The purpose of this study is to investigate whether the high energy FFF beam can produce the same plan quality as the conventional low energy flat beam, using a volumetric modulated arc (VMAT) technique for prostate patients. Methods: Ten prostate cancer patients were selected with a prescription of 78Gy. For each patient, three plans were created: (a) double arc flat 6MV plan used clinically; (b) double arc 10MV FFF plan; (c) single arc 10MV FFF plan. Each plan was prescribed so that at least 95% of the PTV received the prescription dose. The following dosimetric endpoints were evaluated: volume receiving 78Gy (V78) of the CTV and PTV, PTV conformality index (CI, ratio of prescription isodose volume to the PTV volume), bladder volume receiving 70Gy (V70) and 60Gy (V60), rectum volume receiving 70Gy (V70) and 50Gy (V50), dose to 10cc of the rectum, and volume of both femoral heads receiving 50Gy (V50). Total monitor units for each plan were recorded. Results: No significant difference was found for all dosimetric endpoints between all plans (p>0.05). Compared to the 6MV plans, monitor units were higher with the double arc 10MV FFF plans and lower with the single arc 10MV FFF plans, 29% and 4% respectively. Conclusion: Both single arc and double arc 10MV FFF VMAT can achieve equivalent plan quality as 6MV flat beam double arc treatment plans. With the gantry speed restriction, a high dose rate of 2400MU/min may allow the optimizer to use more MUs than actually needed. Single arc 10MV FFF VMAT plans are a reasonable alternative to double arc 6MV flat beam VMAT plans.

A light-weight compact proton gantry design with a novel dose delivery system for broad-energetic laser-accelerated beams.

Science.gov (United States)

Masood, U; Cowan, T E; Enghardt, W; Hofmann, K M; Karsch, L; Kroll, F; Schramm, U; Wilkens, J J; Pawelke, J

2017-07-07

Proton beams may provide superior dose-conformity in radiation therapy. However, the large sizes and costs limit the widespread use of proton therapy (PT). The recent progress in proton acceleration via high-power laser systems has made it a compelling alternative to conventional accelerators, as it could potentially reduce the overall size and cost of the PT facilities. However, the laser-accelerated beams exhibit different characteristics than conventionally accelerated beams, i.e. very intense proton bunches with large divergences and broad-energy spectra. For the application of laser-driven beams in PT, new solutions for beam transport, such as beam capture, integrated energy selection, beam shaping and delivery systems are required due to the specific beam parameters. The generation of these beams are limited by the low repetition rate of high-power lasers and this limitation would require alternative solutions for tumour irradiation which can efficiently utilize the available high proton fluence and broad-energy spectra per proton bunch to keep treatment times short. This demands new dose delivery system and irradiation field formation schemes. In this paper, we present a multi-functional light-weight and compact proton gantry design for laser-driven sources based on iron-less pulsed high-field magnets. This achromatic design includes improved beam capturing and energy selection systems, with a novel beam shaping and dose delivery system, so-called ELPIS. ELPIS system utilizes magnetic fields, instead of physical scatterers, for broadening the spot-size of broad-energetic beams while capable of simultaneously scanning them in lateral directions. To investigate the clinical feasibility of this gantry design, we conducted a treatment planning study with a 3D treatment planning system augmented for the pulsed beams with optimizable broad-energetic widths and selectable beam spot sizes. High quality treatment plans could be achieved with such unconventional beam

A light-weight compact proton gantry design with a novel dose delivery system for broad-energetic laser-accelerated beams

Science.gov (United States)

Masood, U.; Cowan, T. E.; Enghardt, W.; Hofmann, K. M.; Karsch, L.; Kroll, F.; Schramm, U.; Wilkens, J. J.; Pawelke, J.

2017-07-01

Proton beams may provide superior dose-conformity in radiation therapy. However, the large sizes and costs limit the widespread use of proton therapy (PT). The recent progress in proton acceleration via high-power laser systems has made it a compelling alternative to conventional accelerators, as it could potentially reduce the overall size and cost of the PT facilities. However, the laser-accelerated beams exhibit different characteristics than conventionally accelerated beams, i.e. very intense proton bunches with large divergences and broad-energy spectra. For the application of laser-driven beams in PT, new solutions for beam transport, such as beam capture, integrated energy selection, beam shaping and delivery systems are required due to the specific beam parameters. The generation of these beams are limited by the low repetition rate of high-power lasers and this limitation would require alternative solutions for tumour irradiation which can efficiently utilize the available high proton fluence and broad-energy spectra per proton bunch to keep treatment times short. This demands new dose delivery system and irradiation field formation schemes. In this paper, we present a multi-functional light-weight and compact proton gantry design for laser-driven sources based on iron-less pulsed high-field magnets. This achromatic design includes improved beam capturing and energy selection systems, with a novel beam shaping and dose delivery system, so-called ELPIS. ELPIS system utilizes magnetic fields, instead of physical scatterers, for broadening the spot-size of broad-energetic beams while capable of simultaneously scanning them in lateral directions. To investigate the clinical feasibility of this gantry design, we conducted a treatment planning study with a 3D treatment planning system augmented for the pulsed beams with optimizable broad-energetic widths and selectable beam spot sizes. High quality treatment plans could be achieved with such unconventional beam

Comparison of VMAT and IMRT strategies for cervical cancer patients using automated planning.

Science.gov (United States)

Sharfo, Abdul Wahab M; Voet, Peter W J; Breedveld, Sebastiaan; Mens, Jan Willem M; Hoogeman, Mischa S; Heijmen, Ben J M

2015-03-01

In a published study on cervical cancer, 5-beam IMRT was inferior to single arc VMAT. Here we compare 9, 12, and 20 beam IMRT with single and dual arc VMAT. For each of 10 patients, automated plan generation with the in-house Erasmus-iCycle optimizer was used to assist an expert planner in generating the five plans with the clinical TPS. For each patient, all plans were clinically acceptable with a high and similar PTV coverage. OAR sparing increased when going from 9 to 12 to 20 IMRT beams, and from single to dual arc VMAT. For all patients, 12 and 20 beam IMRT were superior to single and dual arc VMAT, with substantial variations in gain among the study patients. As expected, delivery of VMAT plans was significantly faster than delivery of IMRT plans. Often reported increased plan quality for VMAT compared to IMRT has not been observed for cervical cancer. Twenty and 12 beam IMRT plans had a higher quality than single and dual arc VMAT. For individual patients, the optimal delivery technique depends on a complex trade-off between plan quality and treatment time that may change with introduction of faster delivery systems. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Comparison of VMAT and IMRT strategies for cervical cancer patients using automated planning

International Nuclear Information System (INIS)

Sharfo, Abdul Wahab M.; Voet, Peter W.J.; Breedveld, Sebastiaan; Mens, Jan Willem M.; Hoogeman, Mischa S.; Heijmen, Ben J.M.

2015-01-01

Background and purpose: In a published study on cervical cancer, 5-beam IMRT was inferior to single arc VMAT. Here we compare 9, 12, and 20 beam IMRT with single and dual arc VMAT. Material and methods: For each of 10 patients, automated plan generation with the in-house Erasmus-iCycle optimizer was used to assist an expert planner in generating the five plans with the clinical TPS. Results: For each patient, all plans were clinically acceptable with a high and similar PTV coverage. OAR sparing increased when going from 9 to 12 to 20 IMRT beams, and from single to dual arc VMAT. For all patients, 12 and 20 beam IMRT were superior to single and dual arc VMAT, with substantial variations in gain among the study patients. As expected, delivery of VMAT plans was significantly faster than delivery of IMRT plans. Conclusions: Often reported increased plan quality for VMAT compared to IMRT has not been observed for cervical cancer. Twenty and 12 beam IMRT plans had a higher quality than single and dual arc VMAT. For individual patients, the optimal delivery technique depends on a complex trade-off between plan quality and treatment time that may change with introduction of faster delivery systems

Large planning target volume in whole abdomen radiation therapy in ovarian cancers - a comparison between volumetric arc and fixed beam based intensity modulation in ovarian cancers: a comparison between volumetric arc and fixed beam based intensity modulation

International Nuclear Information System (INIS)

Krishnan, Jayapalan; Rao, Suresh; Hedge, Sanath; Shambhavi

2013-01-01

Aim of this study is to assess dosimetric characteristics of multiple iso-centre volumetric-modulated arc therapy for the treatment of a large PTV in whole abdomen and ovarian cancers and in comparison with IMRT. Two patients with Epithelial Ovarian Cancer (EOC) underwent CT-simulation in supine position with vacuum cushion and acquired CT-image with 3 mm slice thickness. IMRT and VMAT plans were generated with multiple isocenter using Eclipse Planning System (V10.0.39) for (6 MV photon) Varian UNIQUE Performance Linac equipped with a Millennium-120 MLC and optimised with Progressive Resolution optimizer (PRO3) for prescription 36 Gy to the whole abdomen (PTV W AR) and 45 Gy with daily fraction of 1.8 Gy to the pelvis and pelvic nodes (PTV P elvis) with Simultaneous Integrated Boost and calculated with AAA algorithm in 2.5 mm grid resolution. Mean, V 95% , V 90% , V 107% and uniformity number (Uniformity was defined as US-95%=D5%-D95%/D mean ) was calculated for Planning Target Volumes (PTVs). Organs at Risk (OAR's) were analysed statistically in terms of dose and volume. MU and delivery time were compared. Pre-treatment quality assurance was scored with Gamma Agreement Index (GAl) with 3% and 3 mm thresholds with EPID as well as corresponding Dynalog files were generated and analysed. Feasibility and deliverability of VMAT plans showed to be a solution for the treatment planning and delivery for a large PTV volume (PTV-WAR) treatments, surrounded by critical structures such as liver, spinal canal, and kidneys, offering good dosimetric features with significant logistic improvements compared to IMRT. VMAT combines the advantages of faster delivery and lower number of monitor units (MU). It would help to reduce potential risk of secondary malignancy. VMAT(RapidArc) showed to be a solution to WAR treatments offering good dosimetric features with significant logistic improvements compared to IMRT

Correction of the first order beam transport of the SLC Arcs

International Nuclear Information System (INIS)

Walker, N.; Barklow, T.; Emma, P.; Krejcik, P.

1991-05-01

Correction of the first order transport of the SLC Arcs has been made possible by a technique which allows the full 4x4 transport matrix across any section of Arc to be experimentally determined. By the introduction of small closed bumps into each achromat, it is possible to substantially correct first order optical errors, and notably the cross plane coupling at the exit of the Arcs. 4 refs., 3 figs

Successful delivery of adjuvant external beam radiotherapy for ependymoma in a patient with Ondine's curse

International Nuclear Information System (INIS)

Choi, Mehee; Thoma, Miranda; Tolekidis, George; Byrne, Richard W.; Diaz, Aidnag Z.

2015-01-01

Ondine's curse is a rare, potentially life-threatening disorder characterized by loss of automatic breathing during sleep and preserved voluntary breathing. It is seldom encountered in the radiotherapy clinic but can pose significant technical challenges and safety concerns in the delivery of a prescribed radiation course. We report a unique case of successful delivery of radiotherapy for ependymoma in a patient with Ondine's curse. A 53-year-old gentleman presented with vertigo when lying down. Brain magnetic resonance imaging revealed an enhancing mass in the floor of the fourth ventricle. He underwent maximal safe resection. Pathology revealed ependymoma. The patient was referred for radiotherapy. Computed tomography simulation was performed in supine position with 3-point thermoplastic mask immobilization. Sequential TomoTherapy plans were developed. At first scheduled treatment, shortly after mask placement, his arms went limp and he was unresponsive. Vitals showed oxygen saturation 83%, pulse 127, and blood pressure 172/97 mm Hg. He was diagnosed with Ondine's curse thought secondary to previous brainstem damage; the combination of lying flat and pressure from the mask was causing him to go into respiratory arrest. As supine positioning did not seem clinically advisable, he was simulated in prone position. A RapidArc plan and a back-up conformal plan were developed. Prescriptions were modified to meet conservative organs-at-risk constraints. Several strategies were used to minimize uncertainties in set-up reproducibility associated with prone positioning. He tolerated prone RapidArc treatments well. The report highlights the importance of applying practical patient safety and treatment planning/delivery strategies in the management of this challenging case.

SU-F-T-522: Dosimetric Study of Junction Dose in Double Isocenter Flatten and Flatten Filter Free IMRT and VMAT Plan Delivery

Energy Technology Data Exchange (ETDEWEB)

Samuvel, K; Yadav, G; Bhushan, M; Tamilarasu, S; Kumar, L; Suhail, M [Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, Delhi (India)

2016-06-15

Purpose: To quantify the dosimetric accuracy of junction dose in double isocenter flattened and flatten filter free(FFF) intensity modulated radiation therapy(IMRT) and volumetric modulated arc therapy(VMAT) plan delivery using pelvis phantom. Methods: Five large field pelvis patients were selected for this study. Double isocenter IMRT and VMAT treatment plans were generated in Eclipse Treatment planning System (V.11.0) using 6MV FB and FFF beams. For all the plans same distance 17.0cm was kept between one isocenter to another isocenter. IMRT Plans were made with 7 coplanar fields and VMAT plans were made with full double arcs. Dose calculation was performed using AAA algorithms with dose grid size of 0.25 cm. Verification plans were calculated on Scanditronix Wellhofer pelvis slab phantom. Measurement point was selected and calculated, where two isocenter plan fields are overlapping, this measurement point was kept at distance 8.5cm from both isocenter. The plans were delivered using Varian TrueBeamTM machine on pelvis slab phantom. Point dose measurements was carried out using CC13 ion chamber volume of 0.13cm3. Results: The measured junction point dose are compared with TPS calculated dose. The mean difference observed was 4.5%, 6.0%, 4.0% and 7.0% for IMRT-FB,IMRT-FFF, VMAT-FB and VMAT-FFF respectively. The measured dose results shows closer agreement with calculated dose in Flatten beam planning in both IMRT and VMAT, whereas in FFF beam plan dose difference are more compared with flatten beam plan. Conclusion: Dosimetry accuracy of Large Field junction dose difference was found less in Flatten beam compared with FFF beam plan delivery. Even though more dosimetric studies are required to analyse junction dose for FFF beam planning using multiple point dose measurements and fluence map verification in field junction area.

Some considerations concerning volume-modulated arc therapy: a stepping stone towards a general theory

International Nuclear Information System (INIS)

Webb, S; McQuaid, D

2009-01-01

In this paper it is formally shown that the dynamic multileaf collimator (MLC) IMRT delivery technique remains valid if the MLC is supported on a 1D moving platform. It is also shown that, in such circumstances, it is always time preferable to deliver overlapping modulating fields as a single swept field rather than as separate fields. The most general formulism is presented and then related to simpler equations in limiting cases. The paper explains in detail how a 'small-arc approximation' can be invoked to relate the 1D linear theory to the MLC-on-moving-platform-(gantry) delivery technique involving rotation therapy and known as volume-modulated arc therapy (VMAT). It is explained how volume-modulated arc therapy delivered with open unmodulated fields and which can deliver conformal dose distributions can be interpreted as an IMRT delivery. The (Elekta adopted) term VMAT will be used in a generic sense to include a similar (Varian) method known as RapidArc. Approximate expressions are derived for the 'amount of modulation' possible in a VMAT delivery. This paper does not discuss the actual VMAT planning but gives an insight at a deep level into VMAT delivery. No universal theory of VMAT is known in the sense that there is no theory that can predict precisely the performance of a VMAT delivery in terms of the free parameters available (variable gantry speed, variable fluence-delivery rate, set of MLC shapes, MLC orientation, number of arcs, coplanarity versus non-coplanarity, etc). This is in stark contrast to the situation with several other IMRT delivery techniques where such theoretical analyses are known. In this paper we do not provide such a theory; the material presented is a stepping stone on the path towards this.

MO-H-19A-02: Investigation of Modulated Electron Arc (MeArc) Therapy for the Treatment of Scalp Tumors

Energy Technology Data Exchange (ETDEWEB)

Eldib, A [Fox Chase Cancer Center, Philadelphia, PA (United States); Al-Azhar University, Cairo (Egypt); Jin, L; Martin, J; Li, J; Chibani, O; Galloway, T; Ma, C [Fox Chase Cancer Center, Philadelphia, PA (United States)

2014-06-15

Purpose: Electron arc therapy has long been proposed as the most suitable technique for the treatment of superficial tumors that follow circularly curved surfaces. However it was challenged by unsuitability of the conventional applicators and the lack of adequate 3-D dose calculation tools for arc electron beams in the treatment planning systems (TPS). Now with the availability of an electron specific multi-leaf collimator (eMLC) and an in-house Monte Carlo (MC) based TPS, we were motivated to investigate more advanced modulated electron arc (MeARC) therapy and its beneficial outcome. Methods: We initiated the study by a film measurement conducted in a head and neck phantom, where we delivered electron arcs in a step and shoot manner using the light field as a guide to avoid fields abutments. This step was done to insure enough clearance for the arcs with eMLC. MCBEAM and MCPLAN MC codes were used for the treatment head simulation and phantom dose calculation, respectively. Treatment plans were generated for targets drawn in real patient CTs and head and neck phantom. We utilized beams eye view available from a commercial planning system to create beamlets having same isocenter and adjoined at the scalp surface. Then dose-deposition coefficients from those beamlets were calculated for all electron energies using MCPLAN. An in-house optimization code was then used to find the optimum weights needed from individual beamlets. Results: MeARC showed a nicely tailored dose distribution around the circular curved target on the scalp. Some hot spots were noticed and could be attributed to fields abutment problem owing to the bulging nature of electron profiles. Brain dose was shown to be at lower levels compared to photon treatment. Conclusion: MeARC was shown to be a promising modality for treating scalp cases and could be beneficial to all superficial tumors with a circular curvature.

SU-F-P-28: A Method of Maximize the Noncoplanar Beam Orientations and Assure the Beam Delivery Clearance for Stereotactic Body Radiation Therapy (SBRT)

Energy Technology Data Exchange (ETDEWEB)

Zhu, J [Presence St. Joseph Medical Ctr., Joliet, IL (United States)

2016-06-15

Purpose: Develop a method to maximize the noncoplanar beam orientations and assure the beam delivery clearance for SBRT, therefore, optimize the dose conformality to the target, increase the dose sparing to the critical normal organs and reduce the hot spots in the body. Methods: A SBRT body frame (Elekta, Stockholm, Sweden) was used for patient immobilization and target localization. The SBRT body frame has CT fiducials on its side frames. After patient’s CT scan, the radiation treatment isocenter was defined and its coordinators referring to the body frame was calculated in the radiation treatment planning process. Meanwhile, initial beam orientations were designed based on the patient target and critical organ anatomy. The body frame was put on the linear accelerator couch and positioned to the calculated isocenter. Initially designed beam orientations were manually measured by tuning the body frame position on the couch, the gantry and couch angles. The finalized beam orientations were put into the treatment planning for dosimetric calculations. Results: Without patient presence, an optimal set of beam orientations were designed and validated. The radiation treatment plan was optimized and guaranteed for delivery clearance. Conclusion: The developed method is beneficial and effective in SBRT treatment planning for individual patient. It first allows maximizing the achievable noncoplanar beam orientation space, therefore, optimize the treatment plan for specific patient. It eliminates the risk that a plan needs to be modified due to the gantry and couch collision during patient setup.

Auroral-arc splitting by intrusion of a new convection channel

Directory of Open Access Journals (Sweden)

H. U. Frey

Full Text Available During a run of the Common Programme Three of the EISCAT radar the splitting of an auroral arc was observed by high time-resolution, ground-based cameras when the UHF radar beam was close to the arc. The evening eastward electrojet situation with a large-scale northward ionospheric electric field was disturbed by the intrusion of a convection channel with southward electric field from the east. The interaction of the new convection channel with the auroral arc caused changes in arc brightness and arc splitting, i.e. the creation of a new arc parallel to the pre-existing auroral arc. The event is described as one possibility for the creation of parallel arcs during slightly disturbed magnetic conditions far from the Harang discontinuity.

Auroral-arc splitting by intrusion of a new convection channel

Directory of Open Access Journals (Sweden)

H. U. Frey

1996-12-01

Full Text Available During a run of the Common Programme Three of the EISCAT radar the splitting of an auroral arc was observed by high time-resolution, ground-based cameras when the UHF radar beam was close to the arc. The evening eastward electrojet situation with a large-scale northward ionospheric electric field was disturbed by the intrusion of a convection channel with southward electric field from the east. The interaction of the new convection channel with the auroral arc caused changes in arc brightness and arc splitting, i.e. the creation of a new arc parallel to the pre-existing auroral arc. The event is described as one possibility for the creation of parallel arcs during slightly disturbed magnetic conditions far from the Harang discontinuity.

A 4 MV flattening filter-free beam: commissioning and application to conformal therapy and volumetric modulated arc therapy

International Nuclear Information System (INIS)

Stevens, S W; Rosser, K E; Bedford, J L

2011-01-01

Recent studies have indicated that radiotherapy treatments undertaken on a flattening filter-free (FFF) linear accelerator have a number of advantages over treatments undertaken on a conventional linear accelerator. In addition, 4 MV photon beams may give improved isodose coverage for some treatment volumes at air/tissue interfaces, compared to when utilizing the clinical standard of 6 MV photons. In order to investigate these benefits, FFF beams were established on an Elekta Beam Modulator linear accelerator for 4 MV photons. Commissioning beam data were obtained for open and wedged fields. The measured data were then imported into a treatment planning system and a beam model was commissioned. The beam model was optimized to improve dose calculations at shallow, clinically relevant depths. Following verification, the beam model was utilized in a treatment planning study, including volumetric modulated arc therapy, for a selection of lung, breast/chest wall and larynx patients. Increased dose rates of around 800 MU min -1 were recorded for open fields (relative to 320 MU min -1 for filtered open fields) and reduced head scatter was inferred from output factor measurements. Good agreement between planned and delivered dose was observed in verification of treatment plans. The planning study indicated that with a FFF beam, equivalent (and in some cases improved) isodose profiles could be achieved for small lung and larynx treatment volumes relative to 4 MV filtered treatments. Furthermore, FFF treatments with wedges could be replicated using open fields together with an 'effective wedge' technique and isocentre shift. Clinical feasibility of a FFF beam was therefore demonstrated, with beam modelling, treatment planning and verification being successfully accomplished.

Treatment planning, optimization, and beam delivery technqiues for intensity modulated proton therapy

Science.gov (United States)

Sengbusch, Evan R.

Physical properties of proton interactions in matter give them a theoretical advantage over photons in radiation therapy for cancer treatment, but they are seldom used relative to photons. The primary barriers to wider acceptance of proton therapy are the technical feasibility, size, and price of proton therapy systems. Several aspects of the proton therapy landscape are investigated, and new techniques for treatment planning, optimization, and beam delivery are presented. The results of these investigations suggest a means by which proton therapy can be delivered more efficiently, effectively, and to a much larger proportion of eligible patients. An analysis of the existing proton therapy market was performed. Personal interviews with over 30 radiation oncology leaders were conducted with regard to the current and future use of proton therapy. In addition, global proton therapy market projections are presented. The results of these investigations serve as motivation and guidance for the subsequent development of treatment system designs and treatment planning, optimization, and beam delivery methods. A major factor impacting the size and cost of proton treatment systems is the maximum energy of the accelerator. Historically, 250 MeV has been the accepted value, but there is minimal quantitative evidence in the literature that supports this standard. A retrospective study of 100 patients is presented that quantifies the maximum proton kinetic energy requirements for cancer treatment, and the impact of those results with regard to treatment system size, cost, and neutron production is discussed. This study is subsequently expanded to include 100 cranial stereotactic radiosurgery (SRS) patients, and the results are discussed in the context of a proposed dedicated proton SRS treatment system. Finally, novel proton therapy optimization and delivery techniques are presented. Algorithms are developed that optimize treatment plans over beam angle, spot size, spot spacing

Delivery of modulated electron beams with conventional photon multi-leaf collimators

International Nuclear Information System (INIS)

Klein, Eric E; Mamalui-Hunter, Maria; Low, Daniel A

2009-01-01

Electron beam radiotherapy is an accepted method to treat shallow tumors. However, modulation of electrons to customize dose distributions has not readily been achieved. Studies of bolus and tertiary collimation systems have been met with limitations. We pursue the use of photon multi-leaf collimators (MLC) for modulated electron radiotherapy (MERT) to achieve customized distributions for potential clinical use. As commercial planning systems do not support the use of MLC with electrons, planning was conducted using Monte Carlo calculations. Segmented and dynamic modulated delivery of multiple electron segments was configured, calculated and delivered for validation. Delivery of electrons with segmented or dynamic leaf motion was conducted. A phantom possessing an idealized stepped target was planned and optimized with subsequent validation by measurements. Finally, clinical treatment plans were conducted for post-mastectomy and cutaneous lymphoma of the scalp using forward optimization techniques. Comparison of calculations and measurements was successful with agreement of ±2%/2 mm for the energies, segment sizes, depths tested for delivered segments for the dynamic and segmented delivery. Clinical treatment plans performed provided optimal dose coverage of the target while sparing distal organs at risk. Execution of plans using an anthropomorphic phantom to ensure safe and efficient delivery was conducted. Our study validates that MERT is not only possible using the photon MLC, but the efficient and safe delivery inherent with the dynamic delivery provides an ideal technique for shallow tumor treatment.

Comparison of dose calculations between pencil-beam and Monte Carlo algorithms of the iPlan RT in arc therapy using a homogenous phantom with 3DVH software

International Nuclear Information System (INIS)

Song, Jin Ho; Shin, Hun-Joo; Kay, Chul Seung; Chae, Soo-Min; Son, Seok Hyun

2013-01-01

To create an arc therapy plan, certain current general calculation algorithms such as pencil-beam calculation (PBC) are based on discretizing the continuous arc into multiple fields to simulate an arc. The iPlan RT™ treatment planning system incorporates not only a PBC algorithm, but also a more recent Monte Carlo calculation (MCC) algorithm that does not need beam discretization. The objective of this study is to evaluate the dose differences in a homogenous phantom between PBC and MCC by using a three-dimensional (3D) diode array detector (ArcCHECK™) and 3DVH software. A cylindrically shaped ‘target’ region of interest (ROI) and a ‘periphery ROI’ surrounding the target were designed. An arc therapy plan was created to deliver 600 cGy to the target within a 350° rotation angle, calculated using the PBC and MCC algorithms. The radiation doses were measured by the ArcCHECK, and reproduced by the 3DVH software. Through this process, we could compare the accuracy of both algorithms with regard to the 3D gamma passing rate (for the entire area and for each ROI). Comparing the PBC and MCC planned dose distributions directly, the 3D gamma passing rates for the entire area were 97.7% with the gamma 3%/3 mm criterion. Comparing the planned dose to the measured dose, the 3D gamma passing rates were 98.8% under the PBC algorithm and 100% under the MCC algorithm. The difference was statistically significant (p = 0.034). Furthermore the gamma passing rate decreases 7.5% in the PBC when using the 2%/2 mm criterion compared to only a 0.4% decrease under the MCC. Each ROI as well as the entire area showed statistically significant higher gamma passing rates under the MCC algorithm. The failure points that did not satisfy the gamma criteria showed a regular pattern repeated every 10°. MCC showed better accuracy than the PBC of the iPlan RT in calculating the dose distribution in arc therapy, which was validated with the ArcCHECK and the 3DVH software. This may

Novel dosimetric phantom for quality assurance of volumetric modulated arc therapy

International Nuclear Information System (INIS)

Letourneau, Daniel; Publicover, Julia; Kozelka, Jakub; Moseley, Douglas J.; Jaffray, David A.

2009-01-01

dependence after calibration. For VMAT deliveries, the agreement between measured and calculated doses was good with ≥86.4% of the diodes satisfying 3% of %ΔD or 2 mm DTA for the 180 CP plans. The phantom offered sufficient sensitivity for the detection of small gantry rotation offset (3 deg.) and scaling errors (1 deg.) as well as phantom setup errors of 1 mm, although the results were plan dependent. With its novel geometry, the dosimeter system was also able to experimentally demonstrate the discretization effect of the number of CPs used in the TPS to simulate a continuous arc. These results demonstrate the suitability of the new dosimeter system for the patient-specific QA of VMAT plans and suggest that the dosimeter system can be an effective tool in the routine QA and commissioning of treatment machines capable of VMAT delivery and cone-beam CT image guidance.

Alignment of Duke free electron laser storage ring and optical beam delivery system

International Nuclear Information System (INIS)

Emamian, M.; Hower, N.

1999-01-01

Duke Free Electron Laser Laboratory (DFELL) hosts a 1.1 GeV electron beam storage ring facility which is capable of generating beams in the range of nearly monochromatic gamma rays to high peak power infra red (IR) laser. In this report specifications and procedures for alignment of OK-4 /Duke storage ring FEL wiggler and optical cavity mirrors will be discussed. The OK-4 FEL lasing has demonstrated a series of world record in the last few years. In August of this year the OK-4 FEL successfully commissioned to laser at 193.7 nm. Also in this article, alignment of the γ-ray and UV optical beam delivery system that is currently in progress will be described. (authors)

Electric arc radius and characteristics

International Nuclear Information System (INIS)

Fang, T.M.

1980-01-01

The heat transfer equation of an arc discharge has been solved. The arc is assumed to be a cylinder with negligible axial variation and the dominant heat transfer process is conduction radially inside the column and radiation/convection at the outside edge. The symmetric consideration allows a simple one-dimensional formulation. By taking into account proper variation of the electrical conductivity as function of temperature, the heat balance equation has been solved analytically. The radius of the arc and its current-field characteristics have also been obtained. The conventional results that E approx. I 0 5385 and R approx. I 0 7693 with E being the applied field, I the current, and R the radius of the cylindrical arc, have been proved to be simply limiting cases of our more general characteristics. The results can be applied quite widely including, among others, the neutral beam injection project in nuclear fusion and MHD energy conversion

A comprehensive formulation for volumetric modulated arc therapy planning

Energy Technology Data Exchange (ETDEWEB)

Nguyen, Dan; Lyu, Qihui; Ruan, Dan; O’Connor, Daniel; Low, Daniel A.; Sheng, Ke, E-mail: ksheng@mednet.ucla.edu [Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California 90024 (United States)

2016-07-15

Purpose: Volumetric modulated arc therapy (VMAT) is a widely employed radiation therapy technique, showing comparable dosimetry to static beam intensity modulated radiation therapy (IMRT) with reduced monitor units and treatment time. However, the current VMAT optimization has various greedy heuristics employed for an empirical solution, which jeopardizes plan consistency and quality. The authors introduce a novel direct aperture optimization method for VMAT to overcome these limitations. Methods: The comprehensive VMAT (comVMAT) planning was formulated as an optimization problem with an L2-norm fidelity term to penalize the difference between the optimized dose and the prescribed dose, as well as an anisotropic total variation term to promote piecewise continuity in the fluence maps, preparing it for direct aperture optimization. A level set function was used to describe the aperture shapes and the difference between aperture shapes at adjacent angles was penalized to control MLC motion range. A proximal-class optimization solver was adopted to solve the large scale optimization problem, and an alternating optimization strategy was implemented to solve the fluence intensity and aperture shapes simultaneously. Single arc comVMAT plans, utilizing 180 beams with 2° angular resolution, were generated for a glioblastoma multiforme case, a lung (LNG) case, and two head and neck cases—one with three PTVs (H&N{sub 3PTV}) and one with foue PTVs (H&N{sub 4PTV})—to test the efficacy. The plans were optimized using an alternating optimization strategy. The plans were compared against the clinical VMAT (clnVMAT) plans utilizing two overlapping coplanar arcs for treatment. Results: The optimization of the comVMAT plans had converged within 600 iterations of the block minimization algorithm. comVMAT plans were able to consistently reduce the dose to all organs-at-risk (OARs) as compared to the clnVMAT plans. On average, comVMAT plans reduced the max and mean OAR dose by 6

SU-E-T-514: Investigating the Dose Distributions of Equiangular Spaced Noncoplanar Beams

International Nuclear Information System (INIS)

Mitchell, T; Maxim, P; Hadsell, M; Loo, B

2015-01-01

Purpose It has been demonstrated that the use of noncoplanar beams in radiation therapy may Result in dose distributions that are comparable or better than standard coplanar beams [Pugachev, 2001]. A radiation therapy system designed with a noncoplanar beam geometry could allow for a full ring diagnostic quality imaging system to be placed around the patient. Additionally, if the noncoplanar beams were fixed in number and in their angle with respect to the patient’s axial plane, then both treatment and imaging could be achieved concurrently without the need for moving parts, which could greatly reduce treatment times. For such a system to be designed, it is necessary to determine the appropriate number of beams and the beam angles to achieve optimal dose distributions. For simplicity, the beam angles are assumed to be equiangular in the patient’s axial plane, and only the beam angle with respect to the axial plane are varied. This study aims to investigate the dose distributions produced by equiangular noncoplanar beams for multiple beam numbers and beam angles, and to compare these dose distributions with distributions achieved in coplanar volumetric arc therapy (VMAT). Methods Dose distributions produced by noncoplanar beams were calculated using the Varian Eclipse treatment planning system by varying the gantry, collimator, and couch angles to simulate the noncoplanar delivery method. Noncoplanar intensity-modulated (NC-IMRT) beams using 8, 12, and 16 beams with angles varying from 45 degrees to 54 with respect to the patient’s axial plane were studied. Results The NC-IMRT beams produced dose distributions comparable to VMAT plans for a number of treatment sites, and were capable of meeting similar dose-volume histogram constraints. Conclusion This study has demonstrated that a noncoplanar beam delivery method with fixed beam numbers and beam angles is capable of delivering dose distributions comparable to VMAT plans currently in use

SU-F-T-373: Monte Carlo Versus Pencil Beam Dose Calculation for Spine SBRT Treatments Using HybridARC and Sliding Windows IMRT

Energy Technology Data Exchange (ETDEWEB)

Venencia, C; Pino, M; Caussa, L; Garrigo, E [Instituto de Radioterapia - Fundacion Marie Curie, Cordoba (Argentina); Molineu, A [UT MD Anderson Cancer Center, Houston, TX (United States)

2016-06-15

Purpose: The purpose of this work was to quantify the dosimetric impact of Monte Carlo (MC) dose calculation algorithm compared to Pencil Beam (PB) on Spine SBRT with HybridARC (HA) and sliding windows IMRT (dMLC) treatment modality. Methods: A 6MV beam (1000MU/min) produced by a Novalis TX (BrainLAB-Varian) equipped with HDMLC was used. HA uses 1 arc plus 8 IMRT beams (arc weight between 60–40%) and dIMRT 15 beams. Plans were calculated using iPlan v.4.5.3 (BrainLAB) and the treatment dose prescription was 27Gy in 3 fractions. Dose calculation was done by PB (4mm spatial resolution) with heterogeneity correction and MC dose to water (4mm spatial resolution and 4% mean variance). PTV and spinal cord dose comparison were done. Study was done on 12 patients. IROC Spine Phantom was used to validate HA and quantify dose variation using PB and MC algorithm. Results: The difference between PB and MC for PTV D98%, D95%, Dmean, D2% were 2.6% [−5.1, 6.8], 0.1% [−4.2, 5.4], 0.9% [−1.5, 3.8] and 2.4% [−0.5, 8.3]. The difference between PB and MC for spinal cord Dmax, D1.2cc and D0.35cc were 5.3% [−6.4, 18.4], 9% [−7.0, 17.0] and 7.6% [−0.6, 14.8] respectively. IROC spine phantom shows PTV TLD dose variation of 0.98% for PB and 1.01% for MC. Axial and sagittal film plane gamma index (5%-3mm) was 95% and 97% for PB and 95% and 99% for MC. Conclusion: PB slightly underestimates the dose for the PTV. For the spinal cord PB underestimates the dose and dose differences could be as high as 18% which could have unexpected clinical impact. CI shows no variation between PB and MC for both treatment modalities Treatment modalities have no impact with the dose calculation algorithms used. Following the IROC pass-fail criteria, treatment acceptance requirement was fulfilled for PB and MC.

SU-F-T-185: Study of the Robustness of a Proton Arc Technique Based On PBS Beams

Energy Technology Data Exchange (ETDEWEB)

Wang, Z [Reading Hospital, West Reading, PA (United States); Zheng, Y [Procure Proton Therapy Center, Oklahoma City, OK (United States)

2016-06-15

Purpose: One potential technique to realize proton arc is through using PBS beams from many directions to form overlaid Bragg peak (OBP) spots and placing these OBP spots throughout the target volume to achieve desired dose distribution. In this study, we analyzed the robustness of this proton arc technique. Methods: We used a cylindrical water phantom of 20 cm in radius in our robustness analysis. To study the range uncertainty effect, we changed the density of the phantom by ±3%. To study the setup uncertainty effect, we shifted the phantom by 3 & 5 mm. We also combined the range and setup uncertainties (3mm/±3%). For each test plan, we performed dose calculation for the nominal and 6 disturbed scenarios. Two test plans were used, one with single OBP spot and the other consisting of 121 OBP spots covering a 10×10cm{sup 2} area. We compared the dose profiles between the nominal and disturbed scenarios to estimate the impact of the uncertainties. Dose calculation was performed with Gate/GEANT based Monte Carlo software in cloud computing environment. Results: For each of the 7 scenarios, we simulated 100k & 10M events for plans consisting of single OBP spot and 121 OBP spots respectively. For single OBP spot, the setup uncertainty had minimum impact on the spot’s dose profile while range uncertainty had significant impact on the dose profile. For plan consisting of 121 OBP spots, similar effect was observed but the extent of disturbance was much less compared to single OBP spot. Conclusion: For PBS arc technique, range uncertainty has significantly more impact than setup uncertainty. Although single OBP spot can be severely disturbed by the range uncertainty, the overall effect is much less when a large number of OBP spots are used. Robustness optimization for PBS arc technique should consider range uncertainty with priority.

SU-F-T-185: Study of the Robustness of a Proton Arc Technique Based On PBS Beams

International Nuclear Information System (INIS)

Wang, Z; Zheng, Y

2016-01-01

Purpose: One potential technique to realize proton arc is through using PBS beams from many directions to form overlaid Bragg peak (OBP) spots and placing these OBP spots throughout the target volume to achieve desired dose distribution. In this study, we analyzed the robustness of this proton arc technique. Methods: We used a cylindrical water phantom of 20 cm in radius in our robustness analysis. To study the range uncertainty effect, we changed the density of the phantom by ±3%. To study the setup uncertainty effect, we shifted the phantom by 3 & 5 mm. We also combined the range and setup uncertainties (3mm/±3%). For each test plan, we performed dose calculation for the nominal and 6 disturbed scenarios. Two test plans were used, one with single OBP spot and the other consisting of 121 OBP spots covering a 10×10cm"2 area. We compared the dose profiles between the nominal and disturbed scenarios to estimate the impact of the uncertainties. Dose calculation was performed with Gate/GEANT based Monte Carlo software in cloud computing environment. Results: For each of the 7 scenarios, we simulated 100k & 10M events for plans consisting of single OBP spot and 121 OBP spots respectively. For single OBP spot, the setup uncertainty had minimum impact on the spot’s dose profile while range uncertainty had significant impact on the dose profile. For plan consisting of 121 OBP spots, similar effect was observed but the extent of disturbance was much less compared to single OBP spot. Conclusion: For PBS arc technique, range uncertainty has significantly more impact than setup uncertainty. Although single OBP spot can be severely disturbed by the range uncertainty, the overall effect is much less when a large number of OBP spots are used. Robustness optimization for PBS arc technique should consider range uncertainty with priority.

Flat beams in the SLC

International Nuclear Information System (INIS)

Adolphsen, C.; Barklow, T.; Burke, D.; Decker, F.J.; Emma, P.; Hildreth, M.; Himel, T.; Krejcik, P.; Limberg, T.; Minty, M.

1993-01-01

The Stanford Linear Collider was designed to operate with round beams; horizontal and vertical emittance made equal in the damping rings. The main motivation was to facilitate the optical matching through beam lines with strong coupling elements like the solenoid spin rotator magnets and the SLC arcs. Tests in 1992 showed that open-quote flat close-quote beams with a vertical to horizontal emittance ratio of around 1/10 can be successfully delivered to the end of the linac. Techniques developed to measure and control the coupling of the SLC arcs allow These beams to be transported to the Interaction Point (IP). Before flat beams could be used for collisions with polarized electrons, a new method of rotating the electron spin orientation with vertical arc orbit bumps had to be developed. Early in the 1993 run, the SLC was switched to open-quote flat close-quote beam operation. Within a short time the peak luminosity of the previous running cycle was reached and then surpassed. The average daily luminosity is now a factor of about two higher than the best achieved last year. In the following the authors present an overview of the problems encountered and their solutions for different parts of the SLC

SU-E-T-309: Dosimetric Comparison of Simultaneous Integrated Boost Treatment Plan Between Intensity Modulated Radiotherapies (IMRTs), Dual Arc Volumetric Modulated Arc Therapy (DA-VMAT) and Single Arc Volumetric Modulated Arc Therapy (SA-VMAT) for Nasopharyngeal Carcinoma (NPC)

International Nuclear Information System (INIS)

Sivakumar, R; Janardhan, N; Bhavani, P; Surendran, J; Saranganathan, B; Ibrahim, S; Jhonson, B; Madhuri, B; Anuradha, C

2015-01-01

Purpose: To compare the plan quality and performance of Simultaneous Integrated Boost (SIB) Treatment plan between Seven field (7F) and Nine field(9F) Intensity Modulated Radiotherapies and Single Arc (SA) and Dual Arc (DA) Volumetric Modulated Arc Therapy( VMAT). Methods: Retrospective planning study of 16 patients treated in Elekta Synergy Platform (mlci2) by 9F-IMRT were replanned with 7F-IMRT, Single Arc VMAT and Dual Arc VMAT using CMS, Monaco Treatment Planning System (TPS) with Monte Carlo simulation. Target delineation done as per Radiation Therapy Oncology Protocols (RTOG 0225&0615). Dose Prescribed as 70Gy to Planning Target Volumes (PTV70) and 61Gy to PTV61 in 33 fraction as a SIB technique. Conformity Index(CI), Homogeneity Index(HI) were used as analysis parameter for Target Volumes as well as Mean dose and Max dose for Organ at Risk(OAR,s).Treatment Delivery Time(min), Monitor unit per fraction (MU/fraction), Patient specific quality assurance were also analysed. Results: A Poor dose coverage and Conformity index (CI) was observed in PTV70 by 7F-IMRT among other techniques. SA-VMAT achieved poor dose coverage in PTV61. No statistical significance difference observed in OAR,s except Spinal cord (P= 0.03) and Right optic nerve (P=0.03). DA-VMAT achieved superior target coverage, higher CI (P =0.02) and Better HI (P=0.03) for PTV70 other techniques (7F-IMRT/9F-IMRT/SA-VMAT). A better dose spare for Parotid glands and spinal cord were seen in DA-VMAT. The average treatment delivery time were 5.82mins, 6.72mins, 3.24mins, 4.3mins for 7F-IMRT, 9F-IMRT, SA-VMAT and DA-VMAT respectively. Significance difference Observed in MU/fr (P <0.001) and Patient quality assurance pass rate were >95% (Gamma analysis (Γ3mm, 3%). Conclusion: DA-VAMT showed better target dose coverage and achieved better or equal performance in sparing OARs among other techniques. SA-VMAT offered least Treatment Time than other techniques but achieved poor target coverage. DA-VMAT offered

SU-E-T-309: Dosimetric Comparison of Simultaneous Integrated Boost Treatment Plan Between Intensity Modulated Radiotherapies (IMRTs), Dual Arc Volumetric Modulated Arc Therapy (DA-VMAT) and Single Arc Volumetric Modulated Arc Therapy (SA-VMAT) for Nasopharyngeal Carcinoma (NPC)

Energy Technology Data Exchange (ETDEWEB)

Sivakumar, R; Janardhan, N; Bhavani, P; Surendran, J; Saranganathan, B; Ibrahim, S; Jhonson, B; Madhuri, B [Omega Hospitals, Hyderabad, Telangana (India); Anuradha, C [Vit University, Vellore, Tamil Nadu (India)

2015-06-15

Purpose: To compare the plan quality and performance of Simultaneous Integrated Boost (SIB) Treatment plan between Seven field (7F) and Nine field(9F) Intensity Modulated Radiotherapies and Single Arc (SA) and Dual Arc (DA) Volumetric Modulated Arc Therapy( VMAT). Methods: Retrospective planning study of 16 patients treated in Elekta Synergy Platform (mlci2) by 9F-IMRT were replanned with 7F-IMRT, Single Arc VMAT and Dual Arc VMAT using CMS, Monaco Treatment Planning System (TPS) with Monte Carlo simulation. Target delineation done as per Radiation Therapy Oncology Protocols (RTOG 0225&0615). Dose Prescribed as 70Gy to Planning Target Volumes (PTV70) and 61Gy to PTV61 in 33 fraction as a SIB technique. Conformity Index(CI), Homogeneity Index(HI) were used as analysis parameter for Target Volumes as well as Mean dose and Max dose for Organ at Risk(OAR,s).Treatment Delivery Time(min), Monitor unit per fraction (MU/fraction), Patient specific quality assurance were also analysed. Results: A Poor dose coverage and Conformity index (CI) was observed in PTV70 by 7F-IMRT among other techniques. SA-VMAT achieved poor dose coverage in PTV61. No statistical significance difference observed in OAR,s except Spinal cord (P= 0.03) and Right optic nerve (P=0.03). DA-VMAT achieved superior target coverage, higher CI (P =0.02) and Better HI (P=0.03) for PTV70 other techniques (7F-IMRT/9F-IMRT/SA-VMAT). A better dose spare for Parotid glands and spinal cord were seen in DA-VMAT. The average treatment delivery time were 5.82mins, 6.72mins, 3.24mins, 4.3mins for 7F-IMRT, 9F-IMRT, SA-VMAT and DA-VMAT respectively. Significance difference Observed in MU/fr (P <0.001) and Patient quality assurance pass rate were >95% (Gamma analysis (Γ3mm, 3%). Conclusion: DA-VAMT showed better target dose coverage and achieved better or equal performance in sparing OARs among other techniques. SA-VMAT offered least Treatment Time than other techniques but achieved poor target coverage. DA-VMAT offered

Design status of the NLC beam-delivery system and possible future studies

International Nuclear Information System (INIS)

Zimmermann, F.; Bowden, G.; Burke, D.

1996-10-01

The authors outline some highlights in the present design of the beam-delivery and removal system for the Next Linear Collider (NLC), and present a long list of possible or desirable future studies. On several of the listed items work has already been started since the Snowmass workshop. Other studies could be conducted, for example, in the framework of a conceptual design report (CDR)

On the impact of dose rate variation upon RapidArc implementation of volumetric modulated arc therapy

International Nuclear Information System (INIS)

Nicolini, Giorgia; Clivio, Alessandro; Cozzi, Luca; Fogliata, Antonella; Vanetti, Eugenio

2011-01-01

Purpose: A study was carried out to evaluate the robustness and mutual interplay of two variables concurring to generate modulation patterns of the RapidArc (RapidArc) implementation of volumetric modulated arc therapy. Dose rate (DR) and gantry speed (GS) are free parameters optimized alongside field aperture shape by the RapidArc engine; however, they are limited by machine constraints and mutually compensate in order to deliver the proper MU/deg during the gantry rotation. Methods: Four test cases (one geometrical and three clinical) were selected and RapidArc plans were optimized using maximum allowed dose rates from 100 to 600 MU/min. The maximum gantry speed was fixed at 4.8 deg/s. Qualitative analysis of DR and GS patterns from these cases was summarized together with quantitative assessment of delivery parameters. Pretreatment quality assurance measurements and scoring of plan quality aimed to determine whether preferable initial conditions might be identified or the optimization engine might be invariant to those variables and capable of providing adequate plans independently from the limits applied. Results: The results of the study were: (i) High dynamic range in MU/deg is achievable across all dose rates by means of gantry speed modulation; (ii) there is a robust compensation mechanism between the two variables; (iii) from a machine delivery point-of-view, slightly improved accuracy is achieved when lower DRs are applied; however, this does not have practical consequences since measurements and plan evaluation showed a lack of clinically relevant deviation; and (iv) reduced total treatment time is a major advantage of high DR. Conclusions: A trend toward improved plan quality for clinical cases was observed with high DR but cannot be generalized, due to the limited amount of cases investigated and the consequent limited significance of the observed differences. As a minimum benefit, the reduced total treatment time should be considered as well.

Beam delivery system for Ho:YLF and applications in endodontics

International Nuclear Information System (INIS)

Bachmann, Luciano

2000-01-01

The beam delivery systems, whether using fibers or articulated arms, are very important for the expansion of laser applications into life sciences. This work aims to couple an optical fiber to a home-made Er:Tm:Ho:LiYF 4 laser. For this purpose the beam profile was studied using the beam quality factor M 2 to achieve an homogeneous beam. To determine the M 2 factor, the knife-edge technique was used, relating the laser energy eclipsed by the knife with its transversal position. The resonant cavity was made suitable in order to obtain a stable and homogeneous transversal beam profile, for the optical fiber coupling. It was used a 365 μm diameter core low OH - content fused silica optical fiber, with a proximal SMA-905 connection and a flat distal end. M 2 factors for the Ho:YLF were between 3 and 8, with a non astigmatic beam, although it was observed a divergence asymmetry in the transversal sections. The coupling efficiency was 96%, and in a repeated operation without any adjustment, the new coupling were 82% and 81%. Lasers have being recently used as an adjunct to conventional endodontic preparation to reduce intracanal microbial, preventing reinfection. The knowledge of thermal profile in endodontic procedures is important to determine laser irradiation conditions avoiding periodontal damages. In this sense, the second scope of this work was to use the Ho:YLF system to register the thermal profile in vitro and to compare the results with those obtained with Nd:YAG and Er:YAG commercial lasers. The temperature was recorded in real time through a thermocouple probe at the root apex , resulting in maximum increase of 7 deg C. (author)

The Clinical Value of Non-Coplanar Photon Beams in Biologically Optimized Intensity Modulated Dose Delivery on Deep-Seated Tumours

International Nuclear Information System (INIS)

Ferreira, Brigida C.; Svensson, Roger; Loef, Johan; Brahme, Anders

2003-01-01

The aim of the present study is to compare the merits of different radiobiologically optimized treatment techniques using few-field planar and non-coplanar dose delivery on an advanced cancer of the cervix, with rectum and bladder as principal organs at risk. Classically, the rational for using non-coplanar beams is to minimize the overlap of beam entrance and exit regions and to find new beam directions avoiding organs at risk, in order to reduce damage to sensitive normal tissues. Two four-beam configurations have been extensively studied. The first consists of three evenly spaced coplanar beams and a fourth non-coplanar beam. A second tetrahedral-like configuration, with two symmetric non-coplanar beams at the same gantry angle and two coplanar beams, with optimized beam directions, was also tested. The present study shows that when radiobiologically optimized intensity modulated beams are applied to such a geometry, only a marginal increase in the treatment outcome can be achieved by non-coplanar beams compared to the optimal coplanar treatment. The main reason for this result is that the high dose in the beam-overlap regions is already optimally reduced by biologically optimized intensity modulation in the plane. The large number of degrees of freedom already incorporated in the treatment by the use of intensity modulation and radiobiological optimization, leads to the saturation of the benefit acquired by a further increase in the degrees of freedom with non-coplanar beams. In conclusion, the use coplanar of radiobiologically optimized intensity modulation simplifies the dose delivery, reducing the need for non-coplanar beam portals

Beam Delivery Simulation - Recent Developments and Optimization

CERN Document Server

AUTHOR|(INSPIRE)INSPIRE-00232566; Boogert, Stewart Takashi; Garcia-Morales, H; Gibson, Stephen; Kwee-Hinzmann, Regina; Nevay, Laurence James; Deacon, Lawrence Charles

2015-01-01

Beam Delivery Simulation (BDSIM) is a particle tracking code that simulates the passage of particles through both the magnetic accelerator lattice as well as their interaction with the material of the accelerator itself. The Geant4 toolkit is used to give a full range of physics processes needed to simulate both the interaction of primary particles and the production and subsequent propagation of secondaries. BDSIM has already been used to simulate linear accelerators such as the International Linear Collider (ILC) and the Compact Linear Collider (CLIC), but it has recently been adapted to simulate circular accelerators as well, producing loss maps for the Large Hadron Collider (LHC). In this paper the most recent developments, which extend BDSIM’s functionality as well as improve its efficiency are presented. Improvement and refactorisation of the tracking algorithms are presented alongside improved automatic geometry construction for increased particle tracking speed.

Novel beam delivery fibers for delivering flat-top beams with controlled BPP for high power CW and pulsed laser applications

Science.gov (United States)

Jollivet, C.; Farley, K.; Conroy, M.; Abramczyk, J.; Belke, S.; Becker, F.; Tankala, K.

2016-03-01

Single-mode (SM) kW-class fiber lasers are the tools of choice for material processing applications such as sheet metal cutting and welding. However, application requirements include a flat-top intensity profile and specific beam parameter product (BPP). Here, Nufern introduces a novel specialty fiber technology capable of converting a SM laser beam into a flat-top beam suited for these applications. The performances are demonstrated using a specialty fiber with 100 μm pure silica core, 0.22 NA surrounded by a 120 μm fluorine-doped layer and a 360 μm pure silica cladding, which was designed to match the conventional beam delivery fibers. A SM fiber laser operating at a wavelength of 1.07 μm and terminated with a large-mode area (LMA) fiber with 20 μm core and 0.06 NA was directly coupled in the core of the flat-top specialty fiber using conventional splicing technique. The output beam profile and BPP were characterized first with a low-power source and confirmed using a 2 kW laser and we report a beam transformation from a SM beam into a flat-top intensity profile beam with a 3.8 mm*mrad BPP. This is, to the best of our knowledge, the first successful beam transformation from SM to MM flat-top with controlled BPP in a single fiber integrated in a multi-kW all-fiber system architecture.

Vacuum arc ion charge state distributions

International Nuclear Information System (INIS)

Brown, I.G.; Godechot, X.

1990-06-01

We have measured vacuum arc ion charge state spectra for a wide range of metallic cathode materials. The charge state distributions were measured using a time-of-flight diagnostic to monitor the energetic ion beam produced by a metal vapor vacuum arc ion source. We have obtained data for 48 metallic cathode elements: Li, C, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Sr, Y, Zr, Nb, Mo, Pd, Ag, Cd, In, Sn, Ba, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, Yb, Hf, Ta, W, Ir, Pt, Au, Pb, Bi, Th and U. The arc was operated in a pulsed mode with pulse length 0.25 msec; arc current was 100 A throughout. This array of elements extends and completes previous work by us. In this paper the measured distributions are cataloged and compared with our earlier results and with those of other workers. We also make some observations about the performance of the various elements as suitable vacuum arc cathode materials

Vacuum arc ion charge-state distributions

International Nuclear Information System (INIS)

Brown, I.G.; Godechot, X.

1991-01-01

The authors have measured vacuum arc ion charge-state spectra for a wide range of metallic cathode materials. The charge-state distributions were measured using a time-of-flight diagnostic to monitor the energetic ion beam produced by a metal vapor vacuum arc ion source. They have obtained data for 48 metallic cathode elements: Li, C, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Sr, Y, Zr, Nb, Mo, Pd, Ag, Cd, In, Sn, Ba, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, Yb, Hf, Ta, W, Ir, Pt, Au, Pb, Bi, Th, and U. The arc was operated in a pulsed mode with pulse length 0.25 ms; arc current was 100 A throughout. This array of elements extends and completes previous work by the authors. In this paper the measured distributions are cataloged and compared with their earlier results and those of other workers. They also make some observations about the performance of the various elements as suitable vacuum arc cathode materials

Comparison of carbon stripper foils produced by ARC discharge and laser ablation

Energy Technology Data Exchange (ETDEWEB)

Ophel, T.R.; Rhode, A.; Lobanov, N.; Weisser, D.C.; Turkentine, R.; Wolf, B.; Wlliman, R.G. [Australian National Univ. Canberra, ACT (Australia). Research School of Physical Sciences and Engineering

1998-06-01

The present work describes a series of investigations which compared the arc-deposited foils, prepared at ANU with a batch of foils from Munich, prepared by laser-ablation. The two foil types were bombarded with a beam of 6.8 MeV of {sup 197}Au recording their behaviour and monitoring the total stripped current. Optical and electron spectroscopy was carried out and indicate that the arc-deposited foils were relatively amorphous and smooth, while the laser-ablated foils appears to be much more crystalline. It was found that the average useful lifetimes of the Munich foils were at least ten times longer than arc-deposited foils. Furthermore, they maintained a constant beam output during the time in marked contrast to the arc-deposited foils, for which the output decreased quite rapidly. The longevity, and no less importantly, the constant beam output of the laser-ablated foils have emerged as critical to the continuance of the ERDA program. More significantly though, such qualities have provoked re-examination of likely energies for heavy beams that could be obtained with the Linac booster if foil stripping were used in the 14UD terminal, rather than gas that had previously been considered the only viable option. A program is in progress to explore the means to produce laser-ablated foils, or their equivalent, locally. Extended abstract. 1 ref., 2 figs.

Comparison of carbon stripper foils produced by ARC discharge and laser ablation

International Nuclear Information System (INIS)

Ophel, T.R.; Rhode, A.; Lobanov, N.; Weisser, D.C.; Turkentine, R.; Wolf, B.; Wlliman, R.G.

1998-01-01

The present work describes a series of investigations which compared the arc-deposited foils, prepared at ANU with a batch of foils from Munich, prepared by laser-ablation. The two foil types were bombarded with a beam of 6.8 MeV of 197 Au recording their behaviour and monitoring the total stripped current. Optical and electron spectroscopy was carried out and indicate that the arc-deposited foils were relatively amorphous and smooth, while the laser-ablated foils appears to be much more crystalline. It was found that the average useful lifetimes of the Munich foils were at least ten times longer than arc-deposited foils. Furthermore, they maintained a constant beam output during the time in marked contrast to the arc-deposited foils, for which the output decreased quite rapidly. The longevity, and no less importantly, the constant beam output of the laser-ablated foils have emerged as critical to the continuance of the ERDA program. More significantly though, such qualities have provoked re-examination of likely energies for heavy beams that could be obtained with the Linac booster if foil stripping were used in the 14UD terminal, rather than gas that had previously been considered the only viable option. A program is in progress to explore the means to produce laser-ablated foils, or their equivalent, locally

Effect of high power CO2 and Yb:YAG laser radiation on the characteristics of TIG arc in atmospherical pressure argon and helium

Science.gov (United States)

Wu, Shikai; Xiao, Rongshi

2015-04-01

The effects of laser radiation on the characteristics of the DC tungsten inert gas (TIG) arc were investigated by applying a high power slab CO2 laser and a Yb:YAG disc laser. Experiment results reveal that the arc voltage-current curve shifts downwards, the arc column expands, and the arc temperature rises while the high power CO2 laser beam vertically interacts with the TIG arc in argon. With the increase of the laser power, the voltage-current curve of the arc shifts downwards more significantly, and the closer the laser beam impingement on the arc to the cathode, the more the decrease in arc voltage. Moreover, the arc column expansion and the arc temperature rise occur mainly in the region between the laser beam incident position and the anode. However, the arc characteristics hardly change in the cases of the CO2 laser-helium arc and YAG laser-arc interactions. The reason is that the inverse Bremsstrahlung absorption coefficients are greatly different due to the different electron densities of the argon and helium arcs and the different wave lengths of CO2 and YAG lasers.

Successful delivery of adjuvant external beam radiotherapy for ependymoma in a patient with Ondine's curse

Energy Technology Data Exchange (ETDEWEB)

Choi, Mehee [Department of Radiation Oncology, Loyola University Medical Center, Maywood, IL (United States); Thoma, Miranda; Tolekidis, George [Department of Radiation Oncology, Rush University Medical Center, Chicago, IL (United States); Byrne, Richard W. [Department of Neurosurgery, Rush University Medical Center, Chicago, IL (United States); Diaz, Aidnag Z., E-mail: aidnag_diaz@rush.edu [Department of Radiation Oncology, Rush University Medical Center, Chicago, IL (United States); Department of Neurosurgery, Rush University Medical Center, Chicago, IL (United States)

2015-01-01

Ondine's curse is a rare, potentially life-threatening disorder characterized by loss of automatic breathing during sleep and preserved voluntary breathing. It is seldom encountered in the radiotherapy clinic but can pose significant technical challenges and safety concerns in the delivery of a prescribed radiation course. We report a unique case of successful delivery of radiotherapy for ependymoma in a patient with Ondine's curse. A 53-year-old gentleman presented with vertigo when lying down. Brain magnetic resonance imaging revealed an enhancing mass in the floor of the fourth ventricle. He underwent maximal safe resection. Pathology revealed ependymoma. The patient was referred for radiotherapy. Computed tomography simulation was performed in supine position with 3-point thermoplastic mask immobilization. Sequential TomoTherapy plans were developed. At first scheduled treatment, shortly after mask placement, his arms went limp and he was unresponsive. Vitals showed oxygen saturation 83%, pulse 127, and blood pressure 172/97 mm Hg. He was diagnosed with Ondine's curse thought secondary to previous brainstem damage; the combination of lying flat and pressure from the mask was causing him to go into respiratory arrest. As supine positioning did not seem clinically advisable, he was simulated in prone position. A RapidArc plan and a back-up conformal plan were developed. Prescriptions were modified to meet conservative organs-at-risk constraints. Several strategies were used to minimize uncertainties in set-up reproducibility associated with prone positioning. He tolerated prone RapidArc treatments well. The report highlights the importance of applying practical patient safety and treatment planning/delivery strategies in the management of this challenging case.

Direct-current cathodic vacuum arc system with magnetic-field mechanism for plasma stabilization.

Science.gov (United States)

Zhang, H-S; Komvopoulos, K

2008-07-01

Filtered cathodic vacuum arc (FCVA) deposition is characterized by plasma beam directionality, plasma energy adjustment via substrate biasing, macroparticle filtering, and independent substrate temperature control. Between the two modes of FCVA deposition, namely, direct current (dc) and pulsed arc, the dc mode yields higher deposition rates than the pulsed mode. However, maintaining the dc arc discharge is challenging because of its inherent plasma instabilities. A system generating a special configuration of magnetic field that stabilizes the dc arc discharge during film deposition is presented. This magnetic field is also part of the out-of-plane magnetic filter used to focus the plasma beam and prevent macroparticle film contamination. The efficiency of the plasma-stabilizing magnetic-field mechanism is demonstrated by the deposition of amorphous carbon (a-C) films exhibiting significantly high hardness and tetrahedral carbon hybridization (sp3) contents higher than 70%. Such high-quality films cannot be produced by dc arc deposition without the plasma-stabilizing mechanism presented in this study.

Direct-current cathodic vacuum arc system with magnetic-field mechanism for plasma stabilization

International Nuclear Information System (INIS)

Zhang, H.-S.; Komvopoulos, K.

2008-01-01

Filtered cathodic vacuum arc (FCVA) deposition is characterized by plasma beam directionality, plasma energy adjustment via substrate biasing, macroparticle filtering, and independent substrate temperature control. Between the two modes of FCVA deposition, namely, direct current (dc) and pulsed arc, the dc mode yields higher deposition rates than the pulsed mode. However, maintaining the dc arc discharge is challenging because of its inherent plasma instabilities. A system generating a special configuration of magnetic field that stabilizes the dc arc discharge during film deposition is presented. This magnetic field is also part of the out-of-plane magnetic filter used to focus the plasma beam and prevent macroparticle film contamination. The efficiency of the plasma-stabilizing magnetic-field mechanism is demonstrated by the deposition of amorphous carbon (a-C) films exhibiting significantly high hardness and tetrahedral carbon hybridization (sp 3 ) contents higher than 70%. Such high-quality films cannot be produced by dc arc deposition without the plasma-stabilizing mechanism presented in this study

SU-E-T-538: Lung SBRT Dosimetric Comparison of 3D Conformal and RapidArc Planning

International Nuclear Information System (INIS)

Jiang, R; Zhan, L; Osei, E

2015-01-01

Purpose: Dose distributions of RapidArc Plan can be quite different from standard 3D conformal radiation therapy. SBRT plans can be optimized with high conformity or mimic the 3D conformal treatment planning with very high dose in the center of the tumor. This study quantifies the dosimetric differences among 3D conformal plan; flattened beam and FFF beam RapidArc Plans for lung SBRT. Methods: Five lung cancer patients treated with 3D non-coplanar SBRT were randomly selected. All the patients were CT scanned with 4DCT to determine the internal target volume. Abdominal compression was applied to minimize respiratory motion for SBRT patients. The prescription dose was 48 Gy in 4 fractions. The PTV coverage was optimized by two groups of objective function: one with high conformity, another mimicking 3D conformal dose distribution with high dose in the center of PTV. Optimization constraints were set to meet the criteria of the RTOG-0915 protocol. All VMAT plans were optimized with the RapidArc technique using four full arcs in Eclipse treatment planning system. The RapidArc SBRT plans with flattened 6MV beam and 6MV FFF beam were generated and dosimetric results were compared with the previous treated 3D non-coplanar plans. Results: All the RapidArc plans with flattened beam and FFF beam had similar results for the PTV and OARs. For the high conformity optimization group, The DVH of PTV exhibited a steep dose fall-off outside the PTV compared to the 3D non-coplanar plan. However, for the group mimicking the 3D conformal target dose distribution, although the PTV is very similar to the 3D conformal plan, the ITV coverage is better than 3D conformal plan. Conclusion: Due to excellent clinical experiences of 3D conformal SBRT treatment, the Rapid Arc optimization mimicking 3D conformal planning may be suggested for clinical use

Beam Delivery System Dogleg Design and Integration for the International Linear Collider

CERN Document Server

Jones, J

2010-01-01

It is proposed to investigate the option of moving the positron source to the end of the main linac as a part of the central integration in the International Linear Collider(ILC) project. The positron source incorporates an undulator at the end of the main linac and the photons generated in the undulator are transported to the target, located at a distance of around 400 m. The dogleg design has been optimised to provide the required transverse offset at the location of the target and to give minimum emittance growth at 500 GeV. The design of the dogleg, the layout changes and the tolerances on beam tuning as a result of locating this dogleg in the beginning of the beam delivery system (BDS) are presented.

Production of hyperthermal hydrogen atoms by an arc discharge

International Nuclear Information System (INIS)

Samano, E.C.

1993-01-01

A magnetically confined thermal electric arc gas heater has been designed and built as a suitable source of heat for dissociating hydrogen molecules with energy in the range of a few eV. Specifically, the average beam kinetic energy is determined to be 1.5 eV, the dissociation rate is 0.5 atoms per molecule and the atom beam intensity in the forward direction is 1018 atoms/sr-sec. The working pressure in the arc discharge region is from 15 to 25 torr. This novel atom source has been successfully ignited and operated with pure hydrogen during several hours of continuous performance, maintaining its characteristics. The hyperthermal hydrogen atom beam, which is obtained from this source is analyzed and characterized in a high vacuum system, the characterization of the atom beam is accomplished by two different methods: calorimetry and surface ionization. Calorimetic sensor were used for detecting the atom beam by measuring the delivered power of the impinging atoms on the sensor surface. In the second approach an H-surface production backscattering experiment from a low work function surface was conducted. The validity of these two methods is discussed, and the results are compared. The different collision mechanisms to dissociate and ionize hydrogen molecules in the arch discharge are reviewed, as well as the physics of electric arcs. Finally, a Monte Carlo simulation program is used to calculate the ionization probability of low energy atoms perpendicularly reflected from a surface converter, as a model for atom surface ionization

SU-E-T-442: Sensitivity of Quality Assurance Tools to Delivery Errors On a Magnetic Resonance-Imaging Guided Radiation Therapy (MR-IGRT) System

International Nuclear Information System (INIS)

Rodriguez, V; Li, H; Yang, D; Kashani, R; Wooten, H; Mutic, S; Green, O; Dempsey, J

2014-01-01

Purpose: To test the sensitivity of the quality assurance (QA) tools actively used on a clinical MR-IGRT system for potential delivery errors. Methods: Patient-specific QA procedures have been implemented for a commercially available Cobalt-60 MR-IGRT system. The QA tools utilized were a MR-compatible cylindrical diode-array detector (ArcCHECK) with a custom insert which positions an ionization chamber (Exradin A18) in the middle of the device, as well as an in-house treatment delivery verification program. These tools were tested to investigate their sensitivity to delivery errors. For the ArcCHECK and ion chamber, a baseline was established with a static field irradiation to a known dose. Variations of the baseline were investigated which included rotated gantry, altered field size, directional shifts, and different delivery time. In addition, similar variations were tested with the automated delivery verification program that compared the treatment parameters in the machine delivery logs to the ones in the plan. To test the software, a 3-field conformal plan was generated as the baseline. Results: ArcCHECK noted at least a 13% decrease in passing rate from baseline in the following scenarios: gantry rotation of 1 degree from plan, 5mm change in field size, 2mm lateral shift, and delivery time decrease. Ion chamber measurements remained consistent for these variations except for the 5 second decrease in delivery time scenario which resulted in an 8% difference from baseline. The delivery verification software was able to detect and report the simulated errors such as when the gantry was rotated by 0.6 degrees, the beam weighting was changed by a percent, a single multileaf collimator was moved by 1cm, and the dose was changed from 2 to 1.8Gy. Conclusion: The results show that the current tools used for patient specific QA are capable of detecting small errors in RT delivery with presence of magnetic field

A Monte Carlo evaluation of RapidArc dose calculations for oropharynx radiotherapy

International Nuclear Information System (INIS)

Gagne, I M; Ansbacher, W; Zavgorodni, S; Popescu, C; Beckham, W A

2008-01-01

RapidArc(TM), recently released by Varian Medical Systems, is a novel extension of IMRT in which an optimized 3D dose distribution may be delivered in a single gantry rotation of 360 deg. or less. The purpose of this study was to investigate the accuracy of the analytical anisotropic algorithm (AAA), the sole algorithm for photon dose calculations of RapidArc(TM) treatment plans. The clinical site chosen was oropharynx and the associated nodes involved. The VIMC-Arc system, which utilizes BEAMnrc and DOSXYZnrc for particle transport through the linac head and patient CT phantom, was used as a benchmarking tool. As part of this study, the dose for a single static aperture, typical for RapidArc(TM) delivery, was calculated by the AAA, MC and compared with the film. This film measurement confirmed MC modeling of the beam aperture in water. It also demonstrated that the AAA dosimetric error can be as high as 12% near isolated leaf edges and up to 5% at the leaf end. The composite effect of these errors in a full RapidArc(TM) calculation in water involving a C-shaped target and the associated organ at risk produced a 1.5% overprediction of the mean target dose. In our cohort of six patients, the AAA was found, on average, to overestimate the PTV60 coverage at the 95% level in the presence of air cavities by 1.0% (SD = 1.1%). Removing the air cavities from the target volumes reduced these differences by about a factor of 2. The dose to critical structures was also overestimated by the AAA. The mean dose to the spinal cord was higher by 1.8% (SD = 0.8%), while the effective maximum dose (D 2% ) was only 0.2% higher (SD = 0.6%). The mean dose to the parotid glands was overestimated by ∼9%. This study has shown that the accuracy of the AAA for RapidArc(TM) dose calculations, performed at a resolution of 2.5 mm or better, is adequate for clinical use.

High current vacuum arc ion source for heavy ion fusion

International Nuclear Information System (INIS)

Qi, N.; Schein, J.; Gensler, S.; Prasad, R.R.; Krishnan, M.; Brown, I.

1999-01-01

Heavy Ion fusion (HIF) is one of the approaches for the controlled thermonuclear power production. A source of heavy ions with charge states 1+ to 2+, in ∼0.5 A current beams with ∼20 micros pulse widths and ∼10 Hz repetition rates are required. Thermionic sources have been the workhorse for the HIF program to date, but suffer from sloe turn-on, heating problems for large areas, are limited to low (contact) ionization potential elements and offer relatively low ion fluxes with a charge state limited to 1+. Gas injection sources suffer from partial ionization and deleterious neutral gas effects. The above shortcomings of the thermionic ion sources can be overcome by a vacuum arc ion source. The vacuum arc ion source is a good candidate for HIF applications. It is capable of providing ions of various elements and different charge states, in short and long pulse bursts, with low emittance and high beam currents. Under a Phase-I STTR from DOE, the feasibility of the vacuum arc ion source for the HIF applications is investigated. An existing ion source at LBNL was modified to produce ∼0.5 A, ∼60 keV Gd (A∼158) ion beams. The experimental effort concentrated on beam noise reduction, pulse-to-pulse reproducibility and achieving low beam emittance at 0.5 A ion current level. Details of the source development will be reported

Vacuum arc ion sources - micro to macro

International Nuclear Information System (INIS)

MacGill, R.A.; Dickinson, M.R.; Brown, I.G.

1995-08-01

Vacuum arc ion sources provide a convenient tool for the production of intense beams of metal ions. The sources are relatively easy to construct and they can produce beams from all of the solid metals as well as of compounds, alloys and mixtures. We have made a number of different kinds of such sources over the course of our development work at LBL in the past decade, from very small open-quote thumb-size close-quote versions to a very large one with 50-cm diameter extractor. Beam current ranges from a few milliamperes up to almost 10 amperes and extraction voltage from about 1 kV to 100 kV. Multicathode versions have been made so that one can switch between metal ion species simply and quickly. Most of the sources have been operated in a repetitively pulsed mode, and we've tested a dc version also. Here we outline some construction features of the array of vacuum arc ion sources that we've developed and used, and describe their performance and limitations

TH-EF-BRB-09: Total Body Irradiation with Uniform MU and Modulated Arc Segments, UMMS-TBI

Energy Technology Data Exchange (ETDEWEB)

Yi, B; Chung, H; Mutaf, Y; Prado, K [University of Maryland School of Medicine, Baltimore, MD (United States)

2016-06-15

Purpose: To test a novel total body irradiation (TBI) system using conformal partial arc with patient lying on the stationary couch which is biologically equivalent to a moving couch TBI. This improves the scanning field TBI, which is previously presented. Methods: The Uniform MU Modulated arc Segments TBI or UMMS-TBI scans the treatment plane with a constant machine dose rate and a constant gantry rotation speed. A dynamic MLC pattern which moves while gantry rotates has been designed so that the treatment field moves same distance at the treatment plane per each gantry angle, while maintaining same treatment field size (34cm) at the plane. Dose across the plane varies due to the geometric differences including the distance from the source to a point of interest and the different attenuation from the slanted depth which changes the effective depth. Beam intensity is modulated to correct the dose variation across the plane by assigning the number of gantry angles inversely proportional to the uncorrected dose. Results: Measured dose and calculated dose matched within 1 % for central axis and 3% for off axis for various patient scenarios. Dose from different distance does not follow the inverse square relation as it is predicted from calculation. Dose uniformity better than 5% across 180 cm at 10cm depth is achieved by moving the gantry from −55 to +55 deg. Total treatment time for 2 Gy AP/PA fields is 40–50 minutes excluding patient set up time, at the machine dose rate of 200 MU/min. Conclusion: This novel technique, yet accurate but easy to implement enables TBI treatment in a small treatment room with less program development preparation than other techniques. The VMAT function of treatment delivery is not required to modulate beams. One delivery pattern can be used for different patients by changing the monitor units.

Fiber coupled optical spark delivery system

Science.gov (United States)

Yalin, Azer; Willson, Bryan; Defoort, Morgan

2008-08-12

A spark delivery system for generating a spark using a laser beam is provided, the spark delivery system including a laser light source and a laser delivery assembly. The laser delivery assembly includes a hollow fiber and a launch assembly comprising launch focusing optics to input the laser beam in the hollow fiber. In addition, the laser delivery assembly includes exit focusing optics that demagnify an exit beam of laser light from the hollow fiber, thereby increasing the intensity of the laser beam and creating a spark. In accordance with embodiments of the present invention, the assembly may be used to create a spark in a combustion engine. In accordance with other embodiments of the present invention, a method of using the spark delivery system is provided. In addition, a method of choosing an appropriate fiber for creating a spark using a laser beam is also presented.

Capacitated arc routing problem and its extensions in waste collection

International Nuclear Information System (INIS)

Fadzli, Mohammad; Najwa, Nurul; Luis, Martino

2015-01-01

Capacitated arc routing problem (CARP) is the youngest generation of graph theory that focuses on solving the edge/arc routing for optimality. Since many years, operational research devoted to CARP counterpart, known as vehicle routing problem (VRP), which does not fit to several real cases such like waste collection problem and road maintenance. In this paper, we highlighted several extensions of capacitated arc routing problem (CARP) that represents the real-life problem of vehicle operation in waste collection. By purpose, CARP is designed to find a set of routes for vehicles that satisfies all pre-setting constraints in such that all vehicles must start and end at a depot, service a set of demands on edges (or arcs) exactly once without exceeding the capacity, thus the total fleet cost is minimized. We also addressed the differentiation between CARP and VRP in waste collection. Several issues have been discussed including stochastic demands and time window problems in order to show the complexity and importance of CARP in the related industry. A mathematical model of CARP and its new version is presented by considering several factors such like delivery cost, lateness penalty and delivery time

Capacitated arc routing problem and its extensions in waste collection

Energy Technology Data Exchange (ETDEWEB)

Fadzli, Mohammad; Najwa, Nurul [Institut Matematik Kejuruteraan, Universiti Malaysia Perlis, Kampus Pauh Putra, 02600 Arau, Perlis (Malaysia); Luis, Martino [Othman Yeop Abdullah Graduate School of Business, Universiti Utara Malaysia, 06010 Sintok, Kedah (Malaysia)

2015-05-15

Capacitated arc routing problem (CARP) is the youngest generation of graph theory that focuses on solving the edge/arc routing for optimality. Since many years, operational research devoted to CARP counterpart, known as vehicle routing problem (VRP), which does not fit to several real cases such like waste collection problem and road maintenance. In this paper, we highlighted several extensions of capacitated arc routing problem (CARP) that represents the real-life problem of vehicle operation in waste collection. By purpose, CARP is designed to find a set of routes for vehicles that satisfies all pre-setting constraints in such that all vehicles must start and end at a depot, service a set of demands on edges (or arcs) exactly once without exceeding the capacity, thus the total fleet cost is minimized. We also addressed the differentiation between CARP and VRP in waste collection. Several issues have been discussed including stochastic demands and time window problems in order to show the complexity and importance of CARP in the related industry. A mathematical model of CARP and its new version is presented by considering several factors such like delivery cost, lateness penalty and delivery time.

Beam scrubbing of beam pipes during the first commissioning of SuperKEKB

Science.gov (United States)

Suetsugu, Y.; Shibata, K.; Ishibashi, T.; Kanazawa, K.; Shirai, M.; Terui, S.; Hisamatsu, H.

2018-02-01

The first (Phase-1) commissioning of SuperKEKB-an electron-positron collider with asymmetric energies located at KEK, in Tsukuba, Japan-started in February 2016, after more than five years of upgrading work on KEKB, and successfully ended in June of the same year. This paper describes one major task of Phase-1 commissioning: beam scrubbing the surface of the beam pipes, to prepare them for a sufficiently long beam lifetime and low background noise in the next commissioning, when a new particle detector will be installed. The pressure rises per unit beam current (dP/dI [Pa A-1]) were continuously monitored, and the coefficient of photon-stimulated desorption (PSD), η [molecules photon-1], was evaluated in the arc sections. The value of η decreased steadily with the beam dose, as expected. For arc sections in the positron ring, where most of the beam pipes were newly fabricated, the decrease in η against the photon dose (D) was similar to that previously reported; that is: η ∝ D-0.5 ∼ 0.8. At high storage beam currents, the evolution of η was affected by gas desorption resulting from the multipacting of electrons-that is, the electron cloud effect (ECE), which is a phenomenon particular to high-intensity positron rings. For the arc sections in the electron ring, η also decreased smoothly with the photon dose D, approximately as ∝ D-0.8. Given that most of these beam pipes were reused from KEKB, the value of η was much lower than that of the positron ring, and also lower than that of the electron ring of KEKB from the early stages of D. This implies that the surface of the reused beam pipes remembered the conditions in the KEKB, which is a known memory effect. The results obtained for η are compared with those obtained in various other accelerators.

Feasibility study on the verification of actual beam delivery in a treatment room using EPID transit dosimetry

International Nuclear Information System (INIS)

Baek, Tae Seong; Chung, Eun Ji; Son, Jaeman; Yoon, Myonggeun

2014-01-01

The aim of this study is to evaluate the ability of transit dosimetry using commercial treatment planning system (TPS) and an electronic portal imaging device (EPID) with simple calibration method to verify the beam delivery based on detection of large errors in treatment room. Twenty four fields of intensity modulated radiotherapy (IMRT) plans were selected from four lung cancer patients and used in the irradiation of an anthropomorphic phantom. The proposed method was evaluated by comparing the calculated dose map from TPS and EPID measurement on the same plane using a gamma index method with a 3% dose and 3 mm distance-to-dose agreement tolerance limit. In a simulation using a homogeneous plastic water phantom, performed to verify the effectiveness of the proposed method, the average passing rate of the transit dose based on gamma index was high enough, averaging 94.2% when there was no error during beam delivery. The passing rate of the transit dose for 24 IMRT fields was lower with the anthropomorphic phantom, averaging 86.8% ± 3.8%, a reduction partially due to the inaccuracy of TPS calculations for inhomogeneity. Compared with the TPS, the absolute value of the transit dose at the beam center differed by −0.38% ± 2.1%. The simulation study indicated that the passing rate of the gamma index was significantly reduced, to less than 40%, when a wrong field was erroneously irradiated to patient in the treatment room. This feasibility study suggested that transit dosimetry based on the calculation with commercial TPS and EPID measurement with simple calibration can provide information about large errors for treatment beam delivery

Beam brilliance investigation of high current ion beams at GSI heavy ion accelerator facility.

Science.gov (United States)

Adonin, A A; Hollinger, R

2014-02-01

In this work the emittance measurements of high current Ta-beam provided by VARIS (Vacuum Arc Ion Source) ion source are presented. Beam brilliance as a function of beam aperture at various extraction conditions is investigated. Influence of electrostatic ion beam compression in post acceleration gap on the beam quality is discussed. Use of different extraction systems (single aperture, 7 holes, and 13 holes) in order to achieve more peaked beam core is considered. The possible ways to increase the beam brilliance are discussed.

Multi-cathode metal vapor arc ion source

International Nuclear Information System (INIS)

Brown, I.G.; MacGill, R.A.

1988-01-01

This patent describes an apparatus for generating an ion beam. It comprises: a vacuum enclosure; a support member; cathodes; an anode; means for transporting; a source of electrical power; means for producing an electric arc; means for guiding; and means for extracting ions

Feasibility study of a periodic arc compressor in the presence of coherent synchrotron radiation

International Nuclear Information System (INIS)

Di Mitri, S.

2016-01-01

The advent of short electron bunches in high brightness linear accelerators has raised the awareness of the accelerator community to the degradation of the beam transverse emittance by coherent synchrotron radiation (CSR) emitted in magnetic bunch length compressors, transfer lines and turnaround arcs. Beam optics control has been proposed to mitigate that CSR effect. In this article, we enlarge on the existing literature by reviewing the validity of the linear optics approach in a periodic, achromatic arc compressor. We then study the dependence of the CSR-perturbed emittance to beam optics, mean energy, and bunch charge. The analytical findings are compared with particle tracking results. Practical considerations on CSR-induced energy loss and nonlinear particle dynamics are included. As a result, we identify the range of parameters that allows feasibility of an arc compressor for driving, for example, a free electron laser or a linear collider.

Feasibility study of a periodic arc compressor in the presence of coherent synchrotron radiation

Energy Technology Data Exchange (ETDEWEB)

Di Mitri, S.

2016-01-11

The advent of short electron bunches in high brightness linear accelerators has raised the awareness of the accelerator community to the degradation of the beam transverse emittance by coherent synchrotron radiation (CSR) emitted in magnetic bunch length compressors, transfer lines and turnaround arcs. Beam optics control has been proposed to mitigate that CSR effect. In this article, we enlarge on the existing literature by reviewing the validity of the linear optics approach in a periodic, achromatic arc compressor. We then study the dependence of the CSR-perturbed emittance to beam optics, mean energy, and bunch charge. The analytical findings are compared with particle tracking results. Practical considerations on CSR-induced energy loss and nonlinear particle dynamics are included. As a result, we identify the range of parameters that allows feasibility of an arc compressor for driving, for example, a free electron laser or a linear collider.

Hybrid laser-TIG welding, laser beam welding and gas tungsten arc welding of AZ31B magnesium alloy

International Nuclear Information System (INIS)

Liu Liming; Wang Jifeng; Song Gang

2004-01-01

Welding of AZ31B magnesium alloy was carried out using hybrid laser-TIG (LATIG) welding, laser beam welding (LBW) and gas tungsten arc (TIG) welding. The weldability and microstructure of magnesium AZ31B alloy welded using LATIG, LBW and TIG were investigated by OM and EMPA. The experimental results showed that the welding speed of LATIG was higher than that of TIG, which was caught up with LBW. Besides, the penetration of LATIG doubles that of TIG, and was four times that of LBW. In addition, arc stability was improved in hybrid of laser-TIG welding compared with using the TIG welding alone, especially at high welding speed and under low TIG current. It was found that the heat affect zone of joint was only observed in TIG welding, and the size of grains in it was evidently coarse. In fusion zone, the equiaxed grains exist, whose size was the smallest welded by LBW, and was the largest by TIG welding. It was also found that Mg concentration of the fusion zone was lower than that of the base one by EPMA in three welding processes

Commissioning and early experience with a new-generation low-energy linear accelerator with advanced delivery and imaging functionalities

Directory of Open Access Journals (Sweden)

Fogliata Antonella

2011-09-01

Full Text Available Abstract Background A new-generation low-energy linear accelerator (UNIQUE was introduced in the clinical arena during 2009 by Varian Medical Systems. The world's first UNIQUE was installed at Oncology Institute of Southern Switzerland and put into clinical operation in June 2010. The aim of the present contribution was to report experience about its commissioning and first year results from clinical operation. Methods Commissioning data, beam characteristics and the modeling into the treatment planning system were summarized. Imaging system of UNIQUE included a 2D-2D matching capability and tests were performed to identify system repositioning capability. Finally, since the system is capable of delivering volumetric modulated arc therapy with RapidArc, a summary of the tests performed for such modality to assess its performance in preclinical settings and during clinical usage was included. Results Isocenter virtual diameter was measured as less than 0.2 mm. Observed accuracy of isocenter determination and repositioning for 2D-2D matching procedures in image guidance was Conclusions The results of the commissioning tests and of the first period of clinical operation, resulted meeting specifications and having good margins respect to tolerances. UNIQUE was put into operation for all delivery techniques; in particular, as shown by the pre-treatment quality assurance results, it enabled accurate and safe delivery of RapidArc plans.

Gas delivery system and beamline studies for the test beam facility of the Collider Detector at Fermilab

International Nuclear Information System (INIS)

Franke, H.G. III.

1987-12-01

A fixed-target test beam facility has been designed and constructed at the Meson Test (MT) site to support studies of components of the Collider Detector at Fermi National Accelerator Laboratory (CDF). I assisted in the design and constuction of the test beam facility gas delivery system, and I conducted the initial studies to document the ability of the MT beamline to meet the needs of CDF. Analysis of the preliminary performance data on MT beamline components and beam tunes at required particle energies is presented. Preliminary studies show that the MT beamline has the necessary flexibility to satisfy most CDF requirements now

High harmonic terahertz confocal gyrotron with nonuniform electron beam

Energy Technology Data Exchange (ETDEWEB)

Fu, Wenjie; Guan, Xiaotong; Yan, Yang [THz Research Center, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

2016-01-15

The harmonic confocal gyrotron with nonuniform electron beam is proposed in this paper in order to develop compact and high power terahertz radiation source. A 0.56 THz third harmonic confocal gyrotron with a dual arc section nonuniform electron beam has been designed and investigated. The studies show that confocal cavity has extremely low mode density, and has great advantage to operate at high harmonic. Nonuniform electron beam is an approach to improve output power and interaction efficiency of confocal gyrotron. A dual arc beam magnetron injection gun for designed confocal gyrotron has been developed and presented in this paper.

Total body irradiation with an arc and a gravity-oriented compensator

International Nuclear Information System (INIS)

Chui, C.-S.; Fontenla, Doracy P.; Mullokandov, Edward; Kapulsky, Alex; Lo, Y.-C.; Lo, C.-J.

1997-01-01

Purpose: To deliver uniform dose distributions for total-body irradiation (TBI) with an arc field and a gravity-oriented compensator. This technique allows the patient to be treated lying on the floor in a small treatment room. Methods and Materials: Through the sweeping motion of the gantry, a continuous arc field can deliver a large field to a patient lying on the floor. The dose profile, however, would not be uniform if no compensator were used, due to the effects of inverse square variation of beam intensity with distance as well as the slanted depth in patient. To solve this problem, a gravity-oriented compensator made of cerrobend alloy was designed. This compensator has a cross-section of an inverted isosceles triangle, with the apex always pointing downward, due to gravity. By properly selecting the thickness of the compensator, the width of the base, and the distance between the pivots to the base, the difference in the path length through the compensator can be made just right to compensate the effects of inverse-square and slanted depth, thus producing a uniform dose profile. Results: Arc fields with a gravity-oriented compensator were used for 6, 10, 15, and 18 MV photon beams. The arc field can cover a patient with a height up to 180 cm. The field width was chosen from 32 to 40 cm at the machine isocenter. The optimal thickness of the compensator was found to be 2.5 cm, and its base was 25 cm wide. The distance from the pivot points to the flat surface of the compensator proximal to the beam ranges from 13 to 14 cm for different beam energies. The dose uniformity at a depth of 10 cm is within ±5% for all beam energies used in this study. Conclusion: Highly uniform dose profiles for TBI treatments can be delivered with an arc and a gravity-oriented compensator. The proposed technique is simple and versatile. A single compensator can be used for all energies, because the amount of compensation can be adjusted by changing the distance to the pivot and

High-power laser and arc welding of thorium-doped iridium alloys

International Nuclear Information System (INIS)

David, S.A.; Liu, C.T.

1980-05-01

The arc and laser weldabilities of two Ir-0.3% W alloys containing 60 and 200 wt ppM Th have been investigated. The Ir-.03% W alloy containing 200 wt ppM Th is severely prone to hot cracking during gas tungsten-arc welding. Weld metal cracking results from the combined effects of heat-affected zone liquation cracking and solidification cracking. Scanning electron microscopic analysis of the fractured surface revealed patches of low-melting eutectic. The cracking is influenced to a great extent by the fusion zone microstructure and thorium content. The alloy has been welded with a continuous-wave high-power CO 2 laser system with beam power ranging from 5 to 10 kW and welding speeds of 8 to 25 mm/s. Successful laser welds without hot cracking have been obtained in this particular alloy. This is attributable to the highly concentrated heat source available in the laser beam and the refinement in fusion zone microstructure obtained during laser welding. Efforts to refine the fusion zone structure during gas tungsten-arc welding of Ir-0.3 % W alloy containing 60 wt ppM Th were partially successful. Here transverse arc oscillation during gas tungsten-arc welding refines the fusion zone structure to a certain extent. However, microstructural analysis of this alloy's laser welds indicates further refinement in the fusion zone microstructure than in that from the gas tungsten-arc process using arc oscillations. The fusion zone structure of the laser weld is a strong function of welding speed

WE-D-BRA-07: Analysis of ArcCHECK Diode Array Performance for ViewRay Quality Assurance

International Nuclear Information System (INIS)

Ellefson, S; Culberson, W; Bednarz, B; DeWerd, L; Bayouth, J

2015-01-01

Purpose: Discrepancies in absolute dose values have been detected between the ViewRay treatment planning system and ArcCHECK readings when performing delivery quality assurance on the ViewRay system with the ArcCHECK-MR diode array (SunNuclear Corporation). In this work, we investigate whether these discrepancies are due to errors in the ViewRay planning and/or delivery system or due to errors in the ArcCHECK’s readings. Methods: Gamma analysis was performed on 19 ViewRay patient plans using the ArcCHECK. Frequency analysis on the dose differences was performed. To investigate whether discrepancies were due to measurement or delivery error, 10 diodes in low-gradient dose regions were chosen to compare with ion chamber measurements in a PMMA phantom with the same size and shape as the ArcCHECK, provided by SunNuclear. The diodes chosen all had significant discrepancies in absolute dose values compared to the ViewRay TPS. Absolute doses to PMMA were compared between the ViewRay TPS calculations, ArcCHECK measurements, and measurements in the PMMA phantom. Results: Three of the 19 patient plans had 3%/3mm gamma passing rates less than 95%, and ten of the 19 plans had 2%/2mm passing rates less than 95%. Frequency analysis implied a non-random error process. Out of the 10 diode locations measured, ion chamber measurements were all within 2.2% error relative to the TPS and had a mean error of 1.2%. ArcCHECK measurements ranged from 4.5% to over 15% error relative to the TPS and had a mean error of 8.0%. Conclusion: The ArcCHECK performs well for quality assurance on the ViewRay under most circumstances. However, under certain conditions the absolute dose readings are significantly higher compared to the planned doses. As the ion chamber measurements consistently agree with the TPS, it can be concluded that the discrepancies are due to ArcCHECK measurement error and not TPS or delivery system error. This work was funded by the Bhudatt Paliwal Professorship and the

Target tracking using DMLC for volumetric modulated arc therapy: A simulation study

Energy Technology Data Exchange (ETDEWEB)

Sun Baozhou; Rangaraj, Dharanipathy; Papiez, Lech; Oddiraju, Swetha; Yang Deshan; Li, H. Harold [Department of Radiation Oncology, School of Medicine, Washington University, 4921 Parkview Place, St. Louis, Missouri 63110 (United States); Department of Radiation Oncology, Southwestern Medical Center, University of Texas, Dallas, Texas 75390 (United States); Department of Radiation Oncology, School of Medicine, Washington University, 4921 Parkview Place, St. Louis, Missouri 63110 (United States)

2010-12-15

Purpose: Target tracking using dynamic multileaf collimator (DMLC) is a promising approach for intrafraction motion management in radiation therapy. The purpose of this work is to develop a DMLC tracking algorithm capable of delivering volumetric-modulated arc therapy (VMAT) to the targets that experience two-dimensional (2D) rigid motion in the beam's eye view. Methods: The problem of VMAT delivery to moving targets is formulated as a control problem with constraints. The relationships between gantry speed, gantry acceleration, MLC leaf-velocity, dose rate, and target motion are derived. An iterative search algorithm is developed to find numerical solutions for efficient delivery of a specific VMAT plan to the moving target using 2D DMLC tracking. The delivery of five VMAT lung plans is simulated. The planned and delivered fluence maps in the target-reference frame are calculated and compared. Results: The simulation demonstrates that the 2D tracking algorithm is capable of delivering the VMAT plan to a moving target fast and accurately without violating the machine constraints and the integrity of the treatment plan. The average delivery time is only 29 s longer than that of no-tracking delivery, 101 versus 72 s, respectively. The fluence maps are normalized to 200 MU and the average root-mean-square error between the desired and the delivered fluence is 2.1 MU, compared to 14.8 MU for no-tracking and 3.6 MU for one-dimensional tracking. Conclusions: A locally optimal MLC tracking algorithm for VMAT delivery is proposed, aiming at shortest delivery time while maintaining treatment plan invariant. The inconsequential increase of treatment time due to DMLC tracking is clinically desirable, which makes VMAT with DMLC tracking attractive in treating moving tumors.

Total dural irradiation: RapidArc versus static-field IMRT: A case study

Energy Technology Data Exchange (ETDEWEB)

Kelly, Paul J., E-mail: paulj.kelly@hse.ie [Department of Radiation Oncology, Dana Farber/Brigham and Women' s Cancer Center, Harvard Medical School, Boston, MA (United States); Mannarino, Edward; Lewis, John Henry; Baldini, Elizabeth H.; Hacker, Fred L. [Department of Radiation Oncology, Dana Farber/Brigham and Women' s Cancer Center, Harvard Medical School, Boston, MA (United States)

2012-07-01

The purpose of this study was to compare conventional fixed-gantry angle intensity-modulated radiation therapy (IMRT) with RapidArc for total dural irradiation. We also hypothesize that target volume-individualized collimator angles may produce substantial normal tissue sparing when planning with RapidArc. Five-, 7-, and 9-field fixed-gantry angle sliding-window IMRT plans were generated for comparison with RapidArc plans. Optimization and normal tissue constraints were constant for all plans. All plans were normalized so that 95% of the planning target volume (PTV) received at least 100% of the dose. RapidArc was delivered using 350 Degree-Sign clockwise and counterclockwise arcs. Conventional collimator angles of 45 Degree-Sign and 315 Degree-Sign were compared with 90 Degree-Sign on both arcs. Dose prescription was 59.4 Gy in 33 fractions. PTV metrics used for comparison were coverage, V{sub 107}%, D1%, conformality index (CI{sub 95}%), and heterogeneity index (D{sub 5}%-D{sub 95}%). Brain dose, the main challenge of this case, was compared using D{sub 1}%, Dmean, and V{sub 5} Gy. Dose to optic chiasm, optic nerves, globes, and lenses was also compared. The use of unconventional collimator angles (90 Degree-Sign on both arcs) substantially reduced dose to normal brain. All plans achieved acceptable target coverage. Homogeneity was similar for RapidArc and 9-field IMRT plans. However, heterogeneity increased with decreasing number of IMRT fields, resulting in unacceptable hotspots within the brain. Conformality was marginally better with RapidArc relative to IMRT. Low dose to brain, as indicated by V5Gy, was comparable in all plans. Doses to organs at risk (OARs) showed no clinically meaningful differences. The number of monitor units was lower and delivery time was reduced with RapidArc. The case-individualized RapidArc plan compared favorably with the 9-field conventional IMRT plan. In view of lower monitor unit requirements and shorter delivery time, RapidArc

Relativistic electron-beam transport in curved channels

International Nuclear Information System (INIS)

Vittitoe, C.N.; Morel, J.E.; Wright, T.P.

1982-01-01

Collisionless single particle trajectories are modeled for a single plasma channel having one section curved in a circular arc. The magnetic field is developed by superposition of straight and curved channel segments. The plasma density gives charge and beam-current neutralization. High transport efficiencies are found for turning a relativistic electron beam 90 0 under reasonable conditions of plasma current, beam energy, arc radius, channel radius, and injection distributions in velocity and in position at the channel entrance. Channel exit distributions in velocity and position are found consistent with those for a straight plasma channel of equivalent length. Such transport problems are important in any charged particle-beam application constrained by large diode-to-target distance or by requirements of maximum power deposition in a confined area

Comparison study of intensity modulated arc therapy using single or multiple arcs to intensity modulated radiation therapy for high-risk prostate cancer

International Nuclear Information System (INIS)

Ashamalla, Hani; Tejwani, Ajay; Parameritis, Loannis; Swamy, Uma; Luo, Pei Ching; Guirguis, Adel; Lavaf, Amir

2013-01-01

Intensity modulated arc therapy (IMAT) is a form of intensity modulated radiation therapy (IMRT) that delivers dose in single or multiple arcs. We compared IMRT plans versus single-arc field (1ARC) and multi-arc fields (3ARC) IMAT plans in high-risk prostate cancer. Sixteen patients were studied. Prostate (PTV P ), right pelvic (PTV RtLN ) and left pelvic lymph nodes (PTV LtLN ), and organs at risk were contoured. PTVP, PTV RtLN , and PTV LtLN received 50.40 Gy followed by a boost to PTV B of 28.80 Gy. Three plans were per patient generated: IMRT, 1ARC, and 3ARC. We recorded the dose to the PTV, the mean dose (D MEAN ) to the organs at risk, and volume covered by the 50% isodose. Efficiency was evaluated by monitor units (MU) and beam on time (BOT). Conformity index (CI), Paddick gradient index, and homogeneity index (HI) were also calculated. Average Radiation Therapy Oncology Group CI was 1.17, 1.20, and 1.15 for IMRT, 1ARC, and 3ARC, respectively. The plans' HI were within 1% of each other. The D MEAN of bladder was within 2% of each other. The rectum D MEAN in IMRT plans was 10% lower dose than the arc plans (p < 0.0001). The GI of the 3ARC was superior to IMRT by 27.4% (p = 0.006). The average MU was highest in the IMRT plans (1686) versus 1ARC (575) versus 3ARC (1079). The average BOT was 6 minutes for IMRT compared to 1.3 and 2.9 for 1ARC and 3ARC IMAT (p < 0.05). For high-risk prostate cancer, IMAT may offer a favorable dose gradient profile, conformity, MU and BOT compared to IMRT.

Commissioning and first clinical application of mARC treatment

International Nuclear Information System (INIS)

Dzierma, Yvonne; Nuesken, Frank G.; Kremp, Stephanie; Palm, Jan; Licht, Norbert P.; Ruebe, Christian

2014-01-01

The modulated arc (mARC) technique has recently been introduced for Siemens ARTISTE linear accelerators. We present the first experiences with the commissioning of the system and first patient treatments. Treatment planning and delivery are presented for the Prowess Panther treatment planning system or, alternatively, an in-house code. Dosimetric verification is performed both by point dose measurements and in 3D dose distribution. Depending on the target volume, one or two arcs can be used to create highly conformal plans. Dosimetric verification of the converted mARC plans with step-and-shoot plans shows deviations below 1 % in absolute point dose; in the 3D dose distribution, over 95 % of the points pass the 3D gamma criteria (3 % deviation in local dose and 3 mm distance to agreement for doses > 20 % of the maximum). Patient specific verification of the mARC dose distribution with the calculations has a similar pass rate. Treatment times range between 2 and 5 min for a single arc. To our knowledge, this is the first report of clinical application of the mARC technique. The mARC offers the possibility to save significant amounts of time, with single-arc treatments of only a few minutes achieving comparable dose distribution to IMRT plans taking up to twice as long. (orig.) [de

Modeling skin collimation using the electron pencil beam redefinition algorithm

International Nuclear Information System (INIS)

Chi, Pai-Chun M.; Hogstrom, Kenneth R.; Starkschall, George; Antolak, John A.; Boyd, Robert A.

2005-01-01

Skin collimation is an important tool for electron beam therapy that is used to minimize the penumbra when treating near critical structures, at extended treatment distances, with bolus, or using arc therapy. It is usually made of lead or lead alloy material that conforms to and is placed on patient surface. Presently, commercially available treatment-planning systems lack the ability to model skin collimation and to accurately calculate dose in its presence. The purpose of the present work was to evaluate the use of the pencil beam redefinition algorithm (PBRA) in calculating dose in the presence of skin collimation. Skin collimation was incorporated into the PBRA by terminating the transport of electrons once they enter the skin collimator. Both fixed- and arced-beam dose calculations for arced-beam geometries were evaluated by comparing them with measured dose distributions for 10- and 15-MeV beams. Fixed-beam dose distributions were measured in water at 88-cm source-to-surface distance with an air gap of 32 cm. The 6x20-cm 2 field (dimensions projected to isocenter) had a 10-mm thick lead collimator placed on the surface of the water with its edge 5 cm inside the field's edge located at +10 cm. Arced-beam dose distributions were measured in a 13.5-cm radius polystyrene circular phantom. The beam was arced 90 deg. (-45 deg. to +45 deg. ), and 10-mm thick lead collimation was placed at ±30 deg. . For the fixed beam at 10 MeV, the PBRA-calculated dose agreed with measured dose to within 2.0-mm distance to agreement (DTA) in the regions of high-dose gradient and 2.0% in regions of low dose gradient. At 15 MeV, the PBRA agreed to within a 2.0-mm DTA in the regions of high-dose gradient; however, the PBRA underestimated the dose by as much as 5.3% over small regions at depths less than 2 cm because it did not model electrons scattered from the edge of the skin collimation. For arced beams at 10 MeV, the agreement was 1-mm DTA in the high-dose gradient regions, and 2

SU-E-T-226: Junction Free Craniospinal Irradiation in Linear Accelerator Using Volumetric Modulated Arc Therapy : A Novel Technique Using Dose Tapering

International Nuclear Information System (INIS)

Sarkar, B; Roy, S; Paul, S; Munshi, A; Roy, Shilpi; Jassal, K; Ganesh, T; Mohanti, BK

2014-01-01

Purpose: Spatially separated fields are required for craniospinal irradiation due to field size limitation in linear accelerator. Field junction shits are conventionally done to avoid hot or cold spots. Our study was aimed to demonstrate the feasibility of junction free irradiation plan of craniospinal irradiation (CSI) for Meduloblastoma cases treated in linear accelerator using Volumetric modulated arc therapy (VMAT) technique. Methods: VMAT was planned using multiple isocenters in Monaco V 3.3.0 and delivered in Elekta Synergy linear accelerator. A full arc brain and 40° posterior arc spine fields were planned using two isocentre for short (<1.3 meter height ) and 3 isocentres for taller patients. Unrestricted jaw movement was used in superior-inferior direction. Prescribed dose to PTV was achieved by partial contribution from adjacent beams. A very low dose gradient was generated to taper the isodoses over a long length (>10 cm) at the conventional field junction. Results: In this primary study five patients were planned and three patients were delivered using this novel technique. As the dose contribution from the adjacent beams were varied (gradient) to create a complete dose distribution, therefore there is no specific junction exists in the plan. The junction were extended from 10–14 cm depending on treatment plan. Dose gradient were 9.6±2.3% per cm for brain and 7.9±1.7 % per cm for spine field respectively. Dose delivery error due to positional inaccuracy was calculated for brain and spine field for ±1mm, ±2mm, ±3mm and ±5 mm were 1%–0.8%, 2%–1.6%, 2.8%–2.4% and 4.3%–4% respectively. Conclusion: Dose tapering in junction free CSI do not require a junction shift. Therefore daily imaging for all the field is also not essential. Due to inverse planning dose to organ at risk like thyroid kidney, heart and testis can be reduced significantly. VMAT gives a quicker delivery than Step and shoot or dynamic IMRT

SU-E-T-226: Junction Free Craniospinal Irradiation in Linear Accelerator Using Volumetric Modulated Arc Therapy : A Novel Technique Using Dose Tapering

Energy Technology Data Exchange (ETDEWEB)

Sarkar, B; Roy, S; Paul, S; Munshi, A; Roy, Shilpi; Jassal, K; Ganesh, T; Mohanti, BK [Fortis Memorial Research Institute, Gurgaon (India)

2014-06-01

Purpose: Spatially separated fields are required for craniospinal irradiation due to field size limitation in linear accelerator. Field junction shits are conventionally done to avoid hot or cold spots. Our study was aimed to demonstrate the feasibility of junction free irradiation plan of craniospinal irradiation (CSI) for Meduloblastoma cases treated in linear accelerator using Volumetric modulated arc therapy (VMAT) technique. Methods: VMAT was planned using multiple isocenters in Monaco V 3.3.0 and delivered in Elekta Synergy linear accelerator. A full arc brain and 40° posterior arc spine fields were planned using two isocentre for short (<1.3 meter height ) and 3 isocentres for taller patients. Unrestricted jaw movement was used in superior-inferior direction. Prescribed dose to PTV was achieved by partial contribution from adjacent beams. A very low dose gradient was generated to taper the isodoses over a long length (>10 cm) at the conventional field junction. Results: In this primary study five patients were planned and three patients were delivered using this novel technique. As the dose contribution from the adjacent beams were varied (gradient) to create a complete dose distribution, therefore there is no specific junction exists in the plan. The junction were extended from 10–14 cm depending on treatment plan. Dose gradient were 9.6±2.3% per cm for brain and 7.9±1.7 % per cm for spine field respectively. Dose delivery error due to positional inaccuracy was calculated for brain and spine field for ±1mm, ±2mm, ±3mm and ±5 mm were 1%–0.8%, 2%–1.6%, 2.8%–2.4% and 4.3%–4% respectively. Conclusion: Dose tapering in junction free CSI do not require a junction shift. Therefore daily imaging for all the field is also not essential. Due to inverse planning dose to organ at risk like thyroid kidney, heart and testis can be reduced significantly. VMAT gives a quicker delivery than Step and shoot or dynamic IMRT.

WE-A-207-02: Electron Beam Therapy - Current Status and Future Directions

Energy Technology Data Exchange (ETDEWEB)

Wu, Q. [Duke University Medical Center (United States)

2015-06-15

In memory of the significant contribution of Dr. Jacques Ovadia to electron beam techniques, this session will review recent, advanced techniques which are reinvigorating the science of electron beam radiation therapy. Recent research efforts in improving both the applicability and quality of the electron beam therapy will be discussed, including modulated electron beam radiotherapy (MERT) and dynamic electron arc radiotherapy (DEAR). Learning Objectives: To learn about recent advances in electron beam therapy, including modulated electron beam therapy and dynamic electron arc therapy (DEAR). Put recent advances in the context of work that Dr. Ovadia pursued during his career in medical physics.

WE-A-207-02: Electron Beam Therapy - Current Status and Future Directions

International Nuclear Information System (INIS)

Wu, Q.

2015-01-01

In memory of the significant contribution of Dr. Jacques Ovadia to electron beam techniques, this session will review recent, advanced techniques which are reinvigorating the science of electron beam radiation therapy. Recent research efforts in improving both the applicability and quality of the electron beam therapy will be discussed, including modulated electron beam radiotherapy (MERT) and dynamic electron arc radiotherapy (DEAR). Learning Objectives: To learn about recent advances in electron beam therapy, including modulated electron beam therapy and dynamic electron arc therapy (DEAR). Put recent advances in the context of work that Dr. Ovadia pursued during his career in medical physics

Hybrid laser arc welding: State-of-art review

Science.gov (United States)

Acherjee, Bappa

2018-02-01

Hybrid laser arc welding simultaneously utilizes the arc welding and the laser welding, in a common interaction zone. The synergic effects of laser beam and eclectic arc in the same weld pool results in an increase of welding speed and penetration depth along with the enhancement of gap bridging capability and process stability. This paper presents the current status of this hybrid technique in terms of research, developments and applications. Effort is made to present a comprehensive technical know-how about this process through a systematic review of research articles, industrial catalogues, technical notes, etc. In the introductory part of the review, an overview of the hybrid laser arc welding is presented, including operation principle, process requirements, historical developments, benefits and drawbacks of the process. This is followed by a detailed discussion on control parameters those govern the performance of hybrid laser arc welding process. Thereafter, a report of improvements of performance and weld qualities achieved by using hybrid welding process is presented based on review of several research papers. The succeeding sections furnish the examples of industrial applications and the concluding remarks.

Evaluation of beam delivery and ripple filter design for non-isocentric proton and carbon ion therapy.

Science.gov (United States)

Grevillot, L; Stock, M; Vatnitsky, S

2015-10-21

This study aims at selecting and evaluating a ripple filter design compatible with non-isocentric proton and carbon ion scanning beam treatment delivery for a compact nozzle. The use of non-isocentric treatments when the patient is shifted as close as possible towards the nozzle exit allows for a reduction in the air gap and thus an improvement in the quality of scanning proton beam treatment delivery. Reducing the air gap is less important for scanning carbon ions, but ripple filters are still necessary for scanning carbon ion beams to reduce the number of energy steps required to deliver homogeneous SOBP. The proper selection of ripple filters also allows a reduction in the possible transverse and depth-dose inhomogeneities that could appear in non-isocentric conditions in particular. A thorough review of existing ripple filter designs over the past 16 years is performed and a design for non-isocentric treatment delivery is presented. A unique ripple filter quality index (QIRiFi) independent of the particle type and energy and representative of the ratio between energy modulation and induced scattering is proposed. The Bragg peak width evaluated at the 80% dose level (BPW80) is proposed to relate the energy modulation of the delivered Bragg peaks and the energy layer step size allowing the production of homogeneous SOBP. Gate/Geant4 Monte Carlo simulations have been validated for carbon ion and ripple filter simulations based on measurements performed at CNAO and subsequently used for a detailed analysis of the proposed ripple filter design. A combination of two ripple filters in a series has been validated for non-isocentric delivery and did not show significant transverse and depth-dose inhomogeneities. Non-isocentric conditions allow a significant reduction in the spot size at the patient entrance (up to 350% and 200% for protons and carbon ions with range shifter, respectively), and therefore in the lateral penumbra in the patients.

WE-F-16A-03: 3D Printer Application in Proton Therapy: A Novel Method to Deliver Passive-Scattering Proton Beams with a Fixed Range and Modulation for SRS and SRT

International Nuclear Information System (INIS)

Ding, X; Witztum, A; Liang, X; Reiche, M; Lin, H; Teo, B; Yin, L; Fiene, J; McDonough, J; Kassaee, A

2014-01-01

Purpose: To present a novel technique to deliver passive-scattering proton beam with fixed range and modulation using a 3D printed patient-specific bolus for proton stereotactic radiosurgery and radiotherapy. Methods: A CIRS head phantom was used to simulate a patient with a small brain lesion. A custom bolus was created in the Eclipse Treatment Planning System (TPS) to compensate for the different water equivalent depths from the patient surface to the target from multiple beam directions. To simulate arc therapy, a plan was created on the initial CT using three passive-scattering proton beams with a fixed range and modulations irradiating from different angles. The DICOM-RT structure file of the bolus was exported from the TPS and converted to STL format for 3D printing. The phantom was rescanned with the printed custom bolus and head cup to verify the dose distribution comparing to the initial plan. EBT3 films were placed in the sagital plane of the target to verify the delivered dose distribution. The relative stopping power of the printing material(ABSplus-P430) was measured using the Zebra multi-plate ion chamber. Results: The relative stopping power of the 3D printing material, ABSplus-P430 was 1.05 which is almost water equivalent. The dose difference between verification CT and Initial CT is almost negligible. Film measurement also confirmed the accuracy for this new proton delivery technique. Conclusion: Our method using 3D printed range modifiers simplify the treatment delivery of multiple passive-scattering beams in treatment of small lesion in brain. This technique makes delivery of multiple beam more efficient and can be extended to allow arc therapy with proton beams. The ability to create and construct complex patient specific bolus structures provides a new dimension in creating optimized quality treatment plans not only for proton therapy but also for electron and photon therapy

WE-F-16A-03: 3D Printer Application in Proton Therapy: A Novel Method to Deliver Passive-Scattering Proton Beams with a Fixed Range and Modulation for SRS and SRT

Energy Technology Data Exchange (ETDEWEB)

Ding, X; Witztum, A; Liang, X; Reiche, M; Lin, H; Teo, B; Yin, L; Fiene, J; McDonough, J; Kassaee, A [University Pennsylvania, Philadelphia, PA (United States)

2014-06-15

Purpose: To present a novel technique to deliver passive-scattering proton beam with fixed range and modulation using a 3D printed patient-specific bolus for proton stereotactic radiosurgery and radiotherapy. Methods: A CIRS head phantom was used to simulate a patient with a small brain lesion. A custom bolus was created in the Eclipse Treatment Planning System (TPS) to compensate for the different water equivalent depths from the patient surface to the target from multiple beam directions. To simulate arc therapy, a plan was created on the initial CT using three passive-scattering proton beams with a fixed range and modulations irradiating from different angles. The DICOM-RT structure file of the bolus was exported from the TPS and converted to STL format for 3D printing. The phantom was rescanned with the printed custom bolus and head cup to verify the dose distribution comparing to the initial plan. EBT3 films were placed in the sagital plane of the target to verify the delivered dose distribution. The relative stopping power of the printing material(ABSplus-P430) was measured using the Zebra multi-plate ion chamber. Results: The relative stopping power of the 3D printing material, ABSplus-P430 was 1.05 which is almost water equivalent. The dose difference between verification CT and Initial CT is almost negligible. Film measurement also confirmed the accuracy for this new proton delivery technique. Conclusion: Our method using 3D printed range modifiers simplify the treatment delivery of multiple passive-scattering beams in treatment of small lesion in brain. This technique makes delivery of multiple beam more efficient and can be extended to allow arc therapy with proton beams. The ability to create and construct complex patient specific bolus structures provides a new dimension in creating optimized quality treatment plans not only for proton therapy but also for electron and photon therapy.

Prediction of scaling physics laws for proton acceleration with extended parameter space of the NIF ARC

Science.gov (United States)

Bhutwala, Krish; Beg, Farhat; Mariscal, Derek; Wilks, Scott; Ma, Tammy

2017-10-01

The Advanced Radiographic Capability (ARC) laser at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory is the world's most energetic short-pulse laser. It comprises four beamlets, each of substantial energy ( 1.5 kJ), extended short-pulse duration (10-30 ps), and large focal spot (>=50% of energy in 150 µm spot). This allows ARC to achieve proton and light ion acceleration via the Target Normal Sheath Acceleration (TNSA) mechanism, but it is yet unknown how proton beam characteristics scale with ARC-regime laser parameters. As theory has also not yet been validated for laser-generated protons at ARC-regime laser parameters, we attempt to formulate the scaling physics of proton beam characteristics as a function of laser energy, intensity, focal spot size, pulse length, target geometry, etc. through a review of relevant proton acceleration experiments from laser facilities across the world. These predicted scaling laws should then guide target design and future diagnostics for desired proton beam experiments on the NIF ARC. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and funded by the LLNL LDRD program under tracking code 17-ERD-039.

ALVIN-SeaBeam studies of the Sumisu Rift, Izu-Bonin arc

Science.gov (United States)

Taylor, B.; Brown, G.; Fryer, P.; Gill, J. B.; Hochstaedter, A. G.; Hotta, H.; Langmuir, C. H.; Leinen, M.; Nishimura, A.; Urabe, T.

1990-10-01

Bimodal volcanism, normal faulting, rapid sedimentation, and hydrothermal circulation characterize the rifting of the Izu-Bonin arc at 31°N. Analysis of the zigzag pattern, in plan view, of the normal faults that bound Sumisu Rift indicates that the extension direction (080° ± 10°) is orthogonal to the regional trend of the volcanic front. Normal faults divide the rift into an inner rift on the arc side, which is the locus for maximum subsidence and sedimentation, and an outer rift further west. Transfer zones that link opposing master faults and/or rift flank uplifts further subdivide the rift into three segments along strike. Volcanism is concentrated along the ENE-trending transfer zone which separates the northern and central rift segments. The differential motion across the zone is accommodated by interdigitating north-trending normal faults rather than by ENE-trending oblique-slip faults. Volcanism in the outer rift has built 50-700 m high edifices without summit craters whereas in the inner rift it has formed two multi-vent en echelon ridges (the largest is 600 m high and 16 km long). The volcanism is dominantly basaltic, with compositions reflecting mantle sources little influenced by arc components. An elongate rhyolite dome and low-temperature hydrothermal deposits occur at the en echelon step in the larger ridge, which is located at the intersection of the transfer zone with the inner rift. The chimneys, veins, and crusts are composed of silica, barite and iron oxide, and are of similar composition to the ferruginous chert that mantles the Kuroko deposits. A 1.2-km transect of seven ALVIN heat flow measurements at 30°48.5'N showed that the inner-rift-bounding faults may serve as water recharge zones, but that they are not necessarily areas of focussed hydrothermal outflow, which instead occurs through the thick basin sediments. The rift basin and arc margin sediments are probably dominated by permeable rhyolitic pumice and ash erupted from submarine

Impact of cathode evaporation on a free-burning arc

International Nuclear Information System (INIS)

Etemadi, K.

1990-01-01

In the center of a free-burning, high intensity argon arc at atmospheric pressure, a highly ionized vapor beam of copper has been generated by a continuous feeding of a thin (0.5 and 1 mm diameter) copper wire to the hot surface region of the cathode in the vicinity of the plasma attachment. The copper vapor is carried into the plasma column between the electrodes by the self-magnetic induced plasma flow caused by the conical shape of the cathode. In order to study the vapor beam, the arc is modeled at atmospheric pressure, with a current of 150 A, a gap spacing of 1 cm, a cathode tip of 60 degrees and a copper vapor flow of 1 mg/s. The temperature, mass flow, current flow and Cu concentration are calculated for the entire plasma region. The intensity distribution of CuI spectral line at 5218.2 angstrom is also recorded by emission spectroscopy and compared with the calculated values. The copper vapor in the cathode region has velocities of 210 m/s with a mass concentration of above 90% within 0.5 mm from the arc axis. The vapor passes from the cathode toward the anode with a slight diffusion in the argon plasma. Higher temperatures and current densities in the core of the arc, caused by the cathode evaporation, are calculated

Metallurgical characterization of pulsed current gas tungsten arc, friction stir and laser beam welded AZ31B magnesium alloy joints

International Nuclear Information System (INIS)

Padmanaban, G.; Balasubramanian, V.

2011-01-01

This paper reports the influences of welding processes such as friction stir welding (FSW), laser beam welding (LBW) and pulsed current gas tungsten arc welding (PCGTAW) on mechanical and metallurgical properties of AZ31B magnesium alloy. Optical microscopy, scanning electron microscopy, transmission electron microscopy and X-Ray diffraction technique were used to evaluate the metallurgical characteristics of welded joints. LBW joints exhibited superior tensile properties compared to FSW and PCGTAW joints due to the formation of finer grains in weld region, higher fusion zone hardness, the absence of heat affected zone, presence of uniformly distributed finer precipitates in weld region.

Plasma arc melting of zirconium

International Nuclear Information System (INIS)

Tubesing, P.K.; Korzekwa, D.R.; Dunn, P.S.

1997-01-01

Zirconium, like some other refractory metals, has an undesirable sensitivity to interstitials such as oxygen. Traditionally, zirconium is processed by electron beam melting to maintain minimum interstitial contamination. Electron beam melted zirconium, however, does not respond positively to mechanical processing due to its large grain size. The authors undertook a study to determine if plasma arc melting (PAM) technology could be utilized to maintain low interstitial concentrations and improve the response of zirconium to subsequent mechanical processing. The PAM process enabled them to control and maintain low interstitial levels of oxygen and carbon, produce a more favorable grain structure, and with supplementary off-gassing, improve the response to mechanical forming

Operating characteristics of a new ion source for KSTAR neutral beam injection system.

Science.gov (United States)

Kim, Tae-Seong; Jeong, Seung Ho; Chang, Doo-Hee; Lee, Kwang Won; In, Sang-Ryul

2014-02-01

A new positive ion source for the Korea Superconducting Tokamak Advanced Research neutral beam injection (KSTAR NBI-1) system was designed, fabricated, and assembled in 2011. The characteristics of the arc discharge and beam extraction were investigated using hydrogen and helium gas to find the optimum operating parameters of the arc power, filament voltage, gas pressure, extracting voltage, accelerating voltage, and decelerating voltage at the neutral beam test stand at the Korea Atomic Energy Research Institute in 2012. Based on the optimum operating condition, the new ion source was then conditioned, and performance tests were primarily finished. The accelerator system with enlarged apertures can extract a maximum 65 A ion beam with a beam energy of 100 keV. The arc efficiency and optimum beam perveance, at which the beam divergence is at a minimum, are estimated to be 1.0 A/kW and 2.5 uP, respectively. The beam extraction tests show that the design goal of delivering a 2 MW deuterium neutral beam into the KSTAR Tokamak plasma is achievable.

An EPID-based method for comprehensive verification of gantry, EPID and the MLC carriage positional accuracy in Varian linacs during arc treatments

International Nuclear Information System (INIS)

Rowshanfarzad, Pejman; McGarry, Conor K; Barnes, Michael P; Sabet, Mahsheed; Ebert, Martin A

2014-01-01

In modern radiotherapy, it is crucial to monitor the performance of all linac components including gantry, collimation system and electronic portal imaging device (EPID) during arc deliveries. In this study, a simple EPID-based measurement method has been introduced in conjunction with an algorithm to investigate the stability of these systems during arc treatments with the aim of ensuring the accuracy of linac mechanical performance. The Varian EPID sag, gantry sag, changes in source-to-detector distance (SDD), EPID and collimator skewness, EPID tilt, and the sag in MLC carriages as a result of linac rotation were separately investigated by acquisition of EPID images of a simple phantom comprised of 5 ball-bearings during arc delivery. A fast and robust software package was developed for automated analysis of image data. Twelve Varian linacs of different models were investigated. The average EPID sag was within 1 mm for all tested linacs. All machines showed less than 1 mm gantry sag. Changes in SDD values were within 1.7 mm except for three linacs of one centre which were within 9 mm. Values of EPID skewness and tilt were negligible in all tested linacs. The maximum sag in MLC leaf bank assemblies was around 1 mm. The EPID sag showed a considerable improvement in TrueBeam linacs. The methodology and software developed in this study provide a simple tool for effective investigation of the behaviour of linac components with gantry rotation. It is reproducible and accurate and can be easily performed as a routine test in clinics

An analysis of the ArcCHECK-MR diode array's performance for ViewRay quality assurance.

Science.gov (United States)

Ellefson, Steven T; Culberson, Wesley S; Bednarz, Bryan P; DeWerd, Larry A; Bayouth, John E

2017-07-01

The ArcCHECK-MR diode array utilizes a correction system with a virtual inclinometer to correct the angular response dependencies of the diodes. However, this correction system cannot be applied to measurements on the ViewRay MR-IGRT system due to the virtual inclinometer's incompatibility with the ViewRay's multiple simultaneous beams. Additionally, the ArcCHECK's current correction factors were determined without magnetic field effects taken into account. In the course of performing ViewRay IMRT quality assurance with the ArcCHECK, measurements were observed to be consistently higher than the ViewRay TPS predictions. The goals of this study were to quantify the observed discrepancies and test whether applying the current factors improves the ArcCHECK's accuracy for measurements on the ViewRay. Gamma and frequency analysis were performed on 19 ViewRay patient plans. Ion chamber measurements were performed at a subset of diode locations using a PMMA phantom with the same dimensions as the ArcCHECK. A new method for applying directionally dependent factors utilizing beam information from the ViewRay TPS was developed in order to analyze the current ArcCHECK correction factors. To test the current factors, nine ViewRay plans were altered to be delivered with only a single simultaneous beam and were measured with the ArcCHECK. The current correction factors were applied using both the new and current methods. The new method was also used to apply corrections to the original 19 ViewRay plans. It was found the ArcCHECK systematically reports doses higher than those actually delivered by the ViewRay. Application of the current correction factors by either method did not consistently improve measurement accuracy. As dose deposition and diode response have both been shown to change under the influence of a magnetic field, it can be concluded the current ArcCHECK correction factors are invalid and/or inadequate to correct measurements on the ViewRay system. © 2017 The

4D in-beam positron emission tomography for verification of motion-compensated ion beam therapy

International Nuclear Information System (INIS)

Parodi, Katia; Saito, Nami; Chaudhri, Naved; Richter, Christian; Durante, Marco; Enghardt, Wolfgang; Rietzel, Eike; Bert, Christoph

2009-01-01

Purpose: Clinically safe and effective treatment of intrafractionally moving targets with scanned ion beams requires dedicated delivery techniques such as beam tracking. Apart from treatment delivery, also appropriate methods for validation of the actual tumor irradiation are highly desirable. In this contribution the feasibility of four-dimensionally (space and time) resolved, motion-compensated in-beam positron emission tomography (4DibPET) was addressed in experimental studies with scanned carbon ion beams. Methods: A polymethyl methracrylate block sinusoidally moving left-right in beam's eye view was used as target. Radiological depth changes were introduced by placing a stationary ramp-shaped absorber proximal of the moving target. Treatment delivery was compensated for motion by beam tracking. Time-resolved, motion-correlated in-beam PET data acquisition was performed during beam delivery with tracking the moving target and prolonged after beam delivery first with the activated target still in motion and, finally, with the target at rest. Motion-compensated 4DibPET imaging was implemented and the results were compared to a stationary reference irradiation of the same treatment field. Data were used to determine feasibility of 4DibPET but also to evaluate offline in comparison to in-beam PET acquisition. Results: 4D in-beam as well as offline PET imaging was found to be feasible and offers the possibility to verify the correct functioning of beam tracking. Motion compensation of the imaged β + -activity distribution allows recovery of the volumetric extension of the delivered field for direct comparison with the reference stationary condition. Observed differences in terms of lateral field extension and penumbra in the direction of motion were typically less than 1 mm for both imaging strategies in comparison to the corresponding reference distributions. However, in-beam imaging retained a better spatial correlation of the measured activity with the delivered

STATUS REPORT ON DEVELOPMENT OF A HIGH-SPEED HIGH-INTENSITY MOLECULAR BEAM

Energy Technology Data Exchange (ETDEWEB)

Knuth, Eldon L.

1963-07-15

Status of a high-speed high-intensity molecular beam under development is described. Bases for designs of the several components are presented. Using an arc-heated source and a hypersonic jet, molecular energies exceeding 1 ev and beam intensities of the order of 10/sup 16/ molecules/ cm/sup 2/ sec are anticipated. A two-disk beam chopper and speed selector provides a means for analyzing the speed distribution in the generated beam, for chopping the beam into bursts of nearly monoenergetic molecules suitable for scattering studies using the time-of-flight technique, and for modulating the beam in order to facilitate detection. A through-flow ionization detector possesses the versatility required for scattering studies using the time-of-flight technique. A sorption pump and a turbo pump serve as central components of alternative pumping systems for the collimating chamber. Using the arc-heated source, the converging nozzle, the conduction-radiation-cooled skimmer, the turbo pump (turning at 3400 rpm), the chopperselector (acting only as a chopper), and the detector, an arc-heated beam is generated and detected. (auth)

SU-E-T-542: Comparison of Stereotactic Radiosurgery (SRS) of Brain Lesions Using Gamma Knife, VMAT, IMRT, and Conformal Arcs

International Nuclear Information System (INIS)

Li, S; Charpentier, P; Chan, P; Neicu, T; Miyamoto, C

2014-01-01

Purpose: To compare dose distributions in stereotactic radiation surgery of brain lesions using gamma Knife, VMAT, conformal arcs, and IMRT in order to provide an optimal treatment. Methods: Dose distributions from single shot of 4C model of Gamma Knife at the helmet collimation sizes of 4, 8, 14, and 18 mm in diameter were compared with full arcs with the square shapes of 4×4 (or 5×5), 8×8 (or 10×10), and spherical shapes of 16 or 20 mm in diameter using EDR3 films in the same gamma knife QA phantom. Plans for ten SRS cases with single and multiple lesions were created in gamma knife plans and Pinnacle plans. The external beam plans had enlarged field size by 2-mm and used single conformal full circle arc for solitary lesion and none coplanar arcs/beams for multiple lesions. Coverage, conformity index, dose to critical organs, and integral dose to the brain and nearby critical structures were compared on all plans. Structures and dose matrices were registered in a Velocity deformable image registration system. Results: Single full circle arc from Elekta beam-modulate MLC (4-mm leaf thickness) and agility MLC (5-mm leaf thickness) have larger penumbra and less flatness than that of Gamma Knife single shot. None-coplanar arcs or beams were required to achieve similar dose distribution. In general, Gamma Knife plans provided significant less integral dose than that of linac-based plans. Benefits of IMRT and VMAT versus gamma Knife and conformal arcs were not significant. Conclusion: Our dose measurement and treatment planning evaluation clearly demonstrated dose distribution differences amount current popular SRS modalities for small solitary and multiple brain lesions. The trend of using MLC shape beams or arcs to replace conventional cones should be revisited in order to keep lower integral dose if the late correlates with some radiation-induced side effects. Pilot grant from Elekta LLC

Multipass autogenous electron beam welding

International Nuclear Information System (INIS)

Murphy, J.L.; Mustaleski, T.M. Jr.; Watson, L.C.

1986-01-01

A multipass, autogenous welding procedure was developed for 7.6 mm (0.3 in.) wall thickness Type 304L stainless steel cylinders. The joint geometry has a 1.5 mm (0.06 in.) root-face width and a rectangular stepped groove that is 0.762 mm (0.03 in.) wide at the top of the root face and extends 1.5 mm in height, terminating into a groove width of 1.27 mm which extends to the outside of the 1.27 mm high weld-boss. One weld pass is made on the root, three passes on the 0.762 mm wide groove and three passes to complete the weld. Multipass, autogenous, electron beam welds maintain the characteristic high depth-to-width ratios and low heat input of single-pass, electron beam welds. The increased part distortion (which is still much less than from arc processes) in multipass weldments is corrected by a preweld machined compensation. Mechanical properties of multipass welds compare well with single-pass welds. The yield strength of welds in aluminum alloy 5083 is approximately the same for single-pass or multipass electron beam and gas, metal-arc welds. The incidence and size of porosity is less in multipass electron beam welding of aluminum as compared to gas, metal-arc welds. The multipass, autogenous, electron beam welding method has proven to be a reliable way to make some difficult welds in multilayer parts or in an instance where inside part temperature or weld underbead must be controlled and weld discontinuities must be minimized

TH-EF-BRB-04: 4π Dynamic Conformal Arc Therapy Dynamic Conformal Arc Therapy (DCAT) for SBRT

Energy Technology Data Exchange (ETDEWEB)

Chiu, T; Long, T; Tian, Z.; Yan, Y; Jiang, S; Gu, X [UT Southwestern Medical Center, Dallas, TX (United States); Modiri, A; Sawant, A [University of Maryland in Baltimore, Baltimore, MD (United States)

2016-06-15

Purpose: To develop an efficient and effective trajectory optimization methodology for 4π dynamic conformal arc treatment (4π DCAT) with synchronized gantry and couch motion; and to investigate potential clinical benefits for stereotactic body radiation therapy (SBRT) to breast, lung, liver and spine tumors. Methods: The entire optimization framework for 4π DCAT inverse planning consists of two parts: 1) integer programming algorithm and 2) particle swarm optimization (PSO) algorithm. The integer programming is designed to find an optimal solution for arc delivery trajectory with both couch and gantry rotation, while PSO minimize a non-convex objective function based on the selected trajectory and dose-volume constraints. In this study, control point interaction is explicitly taken into account. Beam trajectory was modeled as a series of control points connected together to form a deliverable path. With linear treatment planning objectives, a mixed-integer program (MIP) was formulated. Under mild assumptions, the MIP is tractable. Assigning monitor units to control points along the path can be integrated into the model and done by PSO. The developed 4π DCAT inverse planning strategy is evaluated on SBRT cases and compared to clinically treated plans. Results: The resultant dose distribution of this technique was evaluated between 3D conformal treatment plan generated by Pinnacle treatment planning system and 4π DCAT on a lung SBRT patient case. Both plans share the same scale of MU, 3038 and 2822 correspondingly to 3D conformal plan and 4π DCAT. The mean doses for most of OARs were greatly reduced at 32% (cord), 70% (esophagus), 2.8% (lung) and 42.4% (stomach). Conclusion: Initial results in this study show the proposed 4π DCAT treatment technique can achieve better OAR sparing and lower MUs, which indicates that the developed technique is promising for high dose SBRT to reduce the risk of secondary cancer.

Plasma Arc Augmented CO2 laser welding

DEFF Research Database (Denmark)

Bagger, Claus; Andersen, Mikkel; Frederiksen, Niels

2001-01-01

In order to reduce the hardness of laser beam welded 2.13 mm medium strength steel CMn 250, a plasma arc has been used simultaneously with a 2.6 kW CO2 laser source. In a number of systematic laboratory tests, the plasma arc current, plasma gas flow and distance to the laser source were varied...... with all laser parameters fixed. The welds were quality assessed and hardness measured transversely to the welding direction in the top, middle and root of the seam. In the seams welded by laser alone, hardness values between 275 and 304 HV1 were measured, about the double of the base material, 150 HV1...

Test of the beam effect on vacuum arc occurrence in a high-gradient accelerating structure for the CLIC project

CERN Document Server

AUTHOR|(CDS)2130409; Gagliardi, Martino

A new generation of lepton colliders capable of reaching TeV energies is pres- ently under development, and to succeed in this task it is necessary to show that the technology for such a machine is available. The Compact Linear Collider (CLIC) is a possible design option among the future lepton collider projects. It consists of two normal-conducting linacs. Accelerating structures with a gradient of the order of 100 MV/m are necessary to reach the required high energies within a reasonable machine length. One of the strictest require- ments for such accelerating structures is a relatively low occurrence of vacuum arcs. CLIC prototype structures have been tested in the past, but only in absence of beam. In order to proof the feasibility of the high gradient technology for building a functional collider, it is necessary to understand the effect of the beam presence on the vacuum breakdowns. Tests of this type have never been performed previously. The main goal of this work is to provide a first measurement of t...

Gamma-index method sensitivity for gauging plan delivery accuracy of volumetric modulated arc therapy.

Science.gov (United States)

Park, Jong In; Park, Jong Min; Kim, Jung-In; Park, So-Yeon; Ye, Sung-Joon

2015-12-01

The aim of this study was to investigate the sensitivity of the gamma-index method according to various gamma criteria for volumetric modulated arc therapy (VMAT). Twenty head and neck (HN) and twenty prostate VMAT plans were retrospectively selected for this study. Both global and local 2D gamma evaluations were performed with criteria of 3%/3 mm, 2%/2 mm, 1%/2 mm and 2%/1 mm. In this study, the global and local gamma-index calculated the differences in doses relative to the maximum dose and the dose at the current measurement point, respectively. Using log files acquired during delivery, the differences in parameters at every control point between the VMAT plans and the log files were acquired. The differences in dose-volumetric parameters between reconstructed VMAT plans using the log files and the original VMAT plans were calculated. The Spearman's rank correlation coefficients (rs) were calculated between the passing rates and those differences. Considerable correlations with statistical significances were observed between global 1%/2 mm, local 1%/2 mm and local 2%/1 mm and the MLC position differences (rs = -0.712, -0.628 and -0.581). The numbers of rs values with statistical significance between the passing rates and the changes in dose-volumetric parameters were largest in global 2%/2 mm (n = 16), global 2%/1 mm (n = 15) and local 2%/1 mm (n = 13) criteria. Local gamma-index method with 2%/1 mm generally showed higher sensitivity to detect deviations between a VMAT plan and the delivery of the VMAT plan. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Optical tuning in the arcs and final focus sections of the Stanford Linear Collider

International Nuclear Information System (INIS)

Bambade, P.S.

1989-03-01

In this thesis, we present the experimental tuning procedures developed for the Arcs and for the Final Focus Section of the Stanford Linear Collider (SLC). Such tuning is necessary to maximize the luminosity, by minimizing the beam size at the interaction point, and to reduce backgrounds in the experiment. In the final Focus Section, the correction strategy must result from the principles of the optical design, which is based on cancellations between second order aberrations, and on the ability to measure micron-size beams typical of the SLC. In the Arcs, the corrections were designed after the initial commissioning, to make the system more error-tolerant, through a modification in the optical design, and to enable adjustments of the beam phase-space a the injection to the Final Focus System, through a harmonic perturbation technique inspired from circular accelerators. Although the overall optimization of the SLC is not entirely finished, an almost optimal set-up has been achieved for the optics of the Arcs and of the Final Focus Section. Beams with transverse sizes close to the nominal ones, of a few microns, have been obtained at the interaction point. We present and discuss our results and the optical limits to the present performance. 24 refs., 25 figs., 2 tabs

Optical tuning in the arcs and final focus sections of the Stanford Linear Collider

Energy Technology Data Exchange (ETDEWEB)

Bambade, P.S.

1989-03-01

In this thesis, we present the experimental tuning procedures developed for the Arcs and for the Final Focus Section of the Stanford Linear Collider (SLC). Such tuning is necessary to maximize the luminosity, by minimizing the beam size at the interaction point, and to reduce backgrounds in the experiment. In the final Focus Section, the correction strategy must result from the principles of the optical design, which is based on cancellations between second order aberrations, and on the ability to measure micron-size beams typical of the SLC. In the Arcs, the corrections were designed after the initial commissioning, to make the system more error-tolerant, through a modification in the optical design, and to enable adjustments of the beam phase-space a the injection to the Final Focus System, through a harmonic perturbation technique inspired from circular accelerators. Although the overall optimization of the SLC is not entirely finished, an almost optimal set-up has been achieved for the optics of the Arcs and of the Final Focus Section. Beams with transverse sizes close to the nominal ones, of a few microns, have been obtained at the interaction point. We present and discuss our results and the optical limits to the present performance. 24 refs., 25 figs., 2 tabs.

Optical tuning of arcs and final focus section of the Standard Linear Collider (SLC)

International Nuclear Information System (INIS)

Bambade, P.

1989-03-01

In this thesis, we present the experimental tuning procedures developed for the Arcs and for the Final Focus Section of the Stanford Linear Collider (SLC). Such tuning is necessary to maximize the luminosity, by minimizing the beam size at the interaction point, and to reduce backgrounds in the experiment. In the final Focus Section, the correction strategy must result from the principles of the optical design, which is based on cancellations between second order aberrations, and on the ability to measure micron-size beams typical of the SLC. In the Arcs, the corrections were designed after the initial commissioning, to make the system more error-tolerant, through a modification in the optical design, and to enable adjustements of the beam phase-space at the injection to the Final Focus System, through a harmonic perturbation technique inspired from circular accelerators. Although the overall optimization of the SLC is not entirely finished, an almost optimal set-up has been achieved for the optics of the Arcs and of the Final Focus Section. Beams with transverse sizes close to the nominal ones, of a few microns, have been obtained at the interaction point. We present and discuss our results and the optical limits to the present performance [fr

Independent monitor unit calculation for intensity modulated radiotherapy using the MIMiC multileaf collimator

International Nuclear Information System (INIS)

Chen Zhe; Xing Lei; Nath, Ravinder

2002-01-01

A self-consistent monitor unit (MU) and isocenter point-dose calculation method has been developed that provides an independent verification of the MU for intensity modulated radiotherapy (IMRT) using the MIMiC (Nomos Corporation) multileaf collimator. The method takes into account two unique features of IMRT using the MIMiC: namely the gantry-dynamic arc delivery of intensity modulated photon beams and the slice-by-slice dose delivery for large tumor volumes. The method converts the nonuniform beam intensity planned at discrete gantry angles of 5 deg. or 10 deg. into conventional nonmodulated beam intensity apertures of elemental arc segments of 1 deg. This approach more closely simulates the actual gantry-dynamic arc delivery by MIMiC. Because each elemental arc segment is of uniform intensity, the MU calculation for an IMRT arc is made equivalent to a conventional arc with gantry-angle dependent beam apertures. The dose to the isocenter from each 1 deg. elemental arc segment is calculated by using the Clarkson scatter summation technique based on measured tissue-maximum-ratio and output factors, independent of the dose calculation model used in the IMRT planning system. For treatments requiring multiple treatment slices, the MU for the arc at each treatment slice takes into account the MU, leakage and scatter doses from other slices. This is achieved by solving a set of coupled linear equations for the MUs of all involved treatment slices. All input dosimetry data for the independent MU/isocenter point-dose calculation are measured directly. Comparison of the MU and isocenter point dose calculated by the independent program to those calculated by the Corvus planning system and to direct measurements has shown good agreement with relative difference less than ±3%. The program can be used as an independent initial MU verification for IMRT plans using the MIMiC multileaf collimators

Accuracy in radiosurgery: The influence of collimator diameters and arc weights on the dose distribution for single target

Energy Technology Data Exchange (ETDEWEB)

Plazas, M S [National Univ. of Colombia (Colombia); Lefkopoulus, D; Schlienger, M [Service de Radiotherapie, Hopital Tenon, Paris (France). Unite de Radiophysique; Merienne, L [Hopital Sainte Anne, Paris (France). Service de Neurochirurgie

1996-08-01

The dosimetric characteristics of mini-beams and dose distributions in beams used for radio surgery defer substantially from beams used in common radiotherapy. The aim of radio surgery is to deliver a high dose to the lesion in one single fraction, while minimizing the dose delivered to the surrounding normal brain tissue. This type of irradiation is performed with a number of continuous arcs located in various corneal (patient sitting) or sagittal (patient in a supine position) inclined planes using a linear accelerator. A treatment planning system should take into account a large number of irradiation parameters such as the collimator diameter, number of arcs, their angular positions, length and weight of the arcs. We analysed the influence of collimator diameters in the range of 6 to 20 mm using 15 MV X-rays and stereo-tactic irradiation of ellipsoidal inclined arterio venous malformations (AVMs) with a single isocenter. Special arc weights were used to obtain an optimized dose distribution with 13 arcs distributed over an angular sector of 120 deg. x 13 deg. In the two studies made we used 3 dimensional dosimetric calculations. The results were used for the treatment of patients and enabled the choice of the optimal irradiation configuration for each patient. (author). 10 refs, 9 figs.

Large volume unresectable locally advanced non-small cell lung cancer: acute toxicity and initial outcome results with rapid arc

Directory of Open Access Journals (Sweden)

Fogliata Antonella

2010-10-01

Full Text Available Abstract Background To report acute toxicity, initial outcome results and planning therapeutic parameters in radiation treatment of advanced lung cancer (stage III with volumetric modulated arcs using RapidArc (RA. Methods Twenty-four consecutive patients were treated with RA. All showed locally advanced non-small cell lung cancer with stage IIIA-IIIB and with large volumes (GTV:299 ± 175 cm3, PTV:818 ± 206 cm3. Dose prescription was 66Gy in 33 fractions to mean PTV. Delivery was performed with two partial arcs with a 6 MV photon beam. Results From a dosimetric point of view, RA allowed us to respect most planning objectives on target volumes and organs at risk. In particular: for GTV D1% = 105.6 ± 1.7%, D99% = 96.7 ± 1.8%, D5%-D95% = 6.3 ± 1.4%; contra-lateral lung mean dose resulted in 13.7 ± 3.9Gy, for spinal cord D1% = 39.5 ± 4.0Gy, for heart V45Gy = 9.0 ± 7.0Gy, for esophagus D1% = 67.4 ± 2.2Gy. Delivery time was 133 ± 7s. At three months partial remission > 50% was observed in 56% of patients. Acute toxicities at 3 months showed 91% with grade 1 and 9% with grade 2 esophageal toxicity; 18% presented grade 1 and 9% with grade 2 pneumonia; no grade 3 acute toxicity was observed. The short follow-up does not allow assessment of local control and progression free survival. Conclusions RA proved to be a safe and advantageous treatment modality for NSCLC with large volumes. Long term observation of patients is needed to assess outcome and late toxicity.

Small field dose delivery evaluations using cone beam optical computed tomography-based polymer gel dosimetry

Directory of Open Access Journals (Sweden)

Timothy Olding

2011-01-01

Full Text Available This paper explores the combination of cone beam optical computed tomography with an N-isopropylacrylamide (NIPAM-based polymer gel dosimeter for three-dimensional dose imaging of small field deliveries. Initial investigations indicate that cone beam optical imaging of polymer gels is complicated by scattered stray light perturbation. This can lead to significant dosimetry failures in comparison to dose readout by magnetic resonance imaging (MRI. For example, only 60% of the voxels from an optical CT dose readout of a 1 l dosimeter passed a two-dimensional Low′s gamma test (at a 3%, 3 mm criteria, relative to a treatment plan for a well-characterized pencil beam delivery. When the same dosimeter was probed by MRI, a 93% pass rate was observed. The optical dose measurement was improved after modifications to the dosimeter preparation, matching its performance with the imaging capabilities of the scanner. With the new dosimeter preparation, 99.7% of the optical CT voxels passed a Low′s gamma test at the 3%, 3 mm criteria and 92.7% at a 2%, 2 mm criteria. The fitted interjar dose responses of a small sample set of modified dosimeters prepared (a from the same gel batch and (b from different gel batches prepared on the same day were found to be in agreement to within 3.6% and 3.8%, respectively, over the full dose range. Without drawing any statistical conclusions, this experiment gives a preliminary indication that intrabatch or interbatch NIPAM dosimeters prepared on the same day should be suitable for dose sensitivity calibration.

TH-C-BRC-03: Emerging Linac Based SRS/SBRT Technologies with Modulated Arc Delivery

International Nuclear Information System (INIS)

Ren, L.

2016-01-01

The delivery techniques for SRS/SBRT have been under rapid developments in recent years, which pose new challenges to medical physicists ranging from planning and quality assurance to imaging and motion management. This educational course will provide a general overview of the latest delivery techniques in SRS/SBRT, and discuss the clinical processes to address the challenges of each technique with special emphasis on dedicated gamma-ray based device, robotic x-band linac-based system and conventional C-arm s-band linac-based SRS systems. (1). Gamma-ray based SRS/SRT: This is the gold standard of intracranial SRS. With the advent of precision imaging guidance and frameless patient positioning capabilities, novel stereoscopic CBCT and automatic dose adaption solution are introduced to the Gamma-ray based SRS for the first time. The first North American system has been approved by the US regulatory for patient treatments in the spring of 2016. (2). Robotic SRS/SBRT system: A number of technological milestones have been developed in the past few years, including variable aperture collimator, sequential optimization technique, and the time reduction technique. Recently, a new robotic model allows the option of a multi-leaf collimator. These technological advances have reduced the treatment time and improved dose conformity significantly and could potentially expand the application of radiosurgery for the treatment of targets not previously suitable for robotic SRS/SBRT or fractionated stereotactic radiotherapy. These technological advances have created new demanding mandates on hardware and patient quality assurance (QA) tasks, as well as the need for updating/educating the physicists in the community on these requirements. (3). Conventional Linac based treatments: Modulated arc therapy (MAT) has gained wide popularities in Linac-based treatments in recent years due to its high delivery efficiency and excellent dose conformities. Recently, MAT has been introduced to

TH-C-BRC-03: Emerging Linac Based SRS/SBRT Technologies with Modulated Arc Delivery

Energy Technology Data Exchange (ETDEWEB)

Ren, L. [Duke University Medical Center (United States)

2016-06-15

The delivery techniques for SRS/SBRT have been under rapid developments in recent years, which pose new challenges to medical physicists ranging from planning and quality assurance to imaging and motion management. This educational course will provide a general overview of the latest delivery techniques in SRS/SBRT, and discuss the clinical processes to address the challenges of each technique with special emphasis on dedicated gamma-ray based device, robotic x-band linac-based system and conventional C-arm s-band linac-based SRS systems. (1). Gamma-ray based SRS/SRT: This is the gold standard of intracranial SRS. With the advent of precision imaging guidance and frameless patient positioning capabilities, novel stereoscopic CBCT and automatic dose adaption solution are introduced to the Gamma-ray based SRS for the first time. The first North American system has been approved by the US regulatory for patient treatments in the spring of 2016. (2). Robotic SRS/SBRT system: A number of technological milestones have been developed in the past few years, including variable aperture collimator, sequential optimization technique, and the time reduction technique. Recently, a new robotic model allows the option of a multi-leaf collimator. These technological advances have reduced the treatment time and improved dose conformity significantly and could potentially expand the application of radiosurgery for the treatment of targets not previously suitable for robotic SRS/SBRT or fractionated stereotactic radiotherapy. These technological advances have created new demanding mandates on hardware and patient quality assurance (QA) tasks, as well as the need for updating/educating the physicists in the community on these requirements. (3). Conventional Linac based treatments: Modulated arc therapy (MAT) has gained wide popularities in Linac-based treatments in recent years due to its high delivery efficiency and excellent dose conformities. Recently, MAT has been introduced to

Study on a negative hydrogen ion source with hot cathode arc discharge.

Science.gov (United States)

Lin, S H; Fang, X; Zhang, H J; Qian, C; Ma, B H; Wang, H; Li, X X; Zhang, X Z; Sun, L T; Zhang, Z M; Yuan, P; Zhao, H W

2014-02-01

A negative hydrogen (H(-)) ion source with hot cathode arc discharge was designed and fabricated as a primary injector for a 10 MeV PET cyclotron at IMP. 1 mA dc H(-) beam with ɛ N, RMS = 0.08 π mm mrad was extracted at 25 kV. Halbach hexapole was adopted to confine the plasma. The state of arc discharge, the parameters including filament current, arc current, gas pressure, plasma electrode bias, and the ratio of I(e(-))/I(H(-)) were experimentally studied. The discussion on the result, and opinions to improve the source were given.

Plasma arc melting of titanium-tantalum alloys

International Nuclear Information System (INIS)

Dunn, P.; Patterson, R.A.; Haun, R.

1994-01-01

Los Alamos has several applications for high temperature, oxidation and liquid-metal corrosion resistant materials. Further, materials property constraints are dictated by a requirement to maintain low density; e.g., less than the density of stainless steel. Liquid metal compatibility and density requirements have driven the research toward the Ti-Ta system with an upper bound of 60 wt% Ta-40 wt% Ti. Initial melting of these materials was performed in a small button arc melter with several hundred grams of material; however, ingot quantities were soon needed. But, refractory metal alloys whose constituents possess very dissimilar densities, melting temperatures and vapor pressures pose significant difficulty and require specialized melting practices. The Ti-Ta alloys fall into this category with the density of tantalum 16.5 g/cc and that of titanium 4.5 g/cc. Melting is further complicated by the high melting point of Ta(3020 C) and the relatively low boiling point of Ti(3287 C). Previous electron beam melting experience with these materials resulted, in extensive vaporization of the titanium and poor chemical homogeneity. Vacuum arc remelting(VAR) was considered as a melting candidate and discarded due to density and vapor pressure issues associated with electron beam. Plasma arc melting offered the ability to supply a cover gas to deal with vapor pressure issues as well as solidification control to help with macrosegregation in the melt and has successfully produced high quality ingots of the Ti-Ta alloys

Dosimetric study comparing volumetric arc modulation with RapidArc and fixed dynamic intensity-modulated radiation therapy for breast cancer radiotherapy after breast-conserving surgery

International Nuclear Information System (INIS)

Tie Jian; Sun Yan; Gong Jian; Han Shukui; Jiang Fan; Wu Hao

2011-01-01

Objective: To compare the dosimetric difference between volumetric are modulation with RapidArc and fixed field dynamic IMRT for breast cancer radiotherapy after breast-conserving surgery. Methods: Twenty patients with early left-sided breast cancer received radiotherapy after breast-conserving surgery. After target definition, treatment planning was performed by RapidArc and two fixed fields dynamic IMRT respectively on the same CT scan. The target dose distribution, homogeneity of the breast, and the irradiation dose and volume for the lungs, heart, and contralateral breast were read in the dose-volume histogram (DVH) and compared between RapidArc and IMRT. The treatment delivery time and monitor units were also compared. Results: In comparison with the IMRT planning,the homogeneity of clinical target volume (CTV), the volume proportion of 95% prescribed dose (V 95% ) was significantly higher by 0.65% in RapidArc (t=5.16, P=0.001), and the V 105% and V 110% were lower by 10.96% and 1.48 % respectively, however, without statistical significance (t=-2.05, P=0.055 and t=-1.33, P=0.197). The conformal index of planning target volume (PTV) by the RapidArc planning was (0.88±0.02), significantly higher than that by the IMRT planning [(0.74±0.03), t=18.54, P<0.001]. The homogeneity index (HI) of PTV by the RapidArc planning was 1.11±0.01, significantly lower than that by the IMRT planning (1.12±0.02, t=-2.44, P=0.02). There were no significant differences in the maximum dose (D max ) and V 20 for the ipsilateral lung between the RapidArc and IMRT planning, but the values of V 10 , V 5 , D min and D mean by RapidArc planning were all significantly higher than those by the IMRT planning (all P<0.01). The values of max dose and V 30 for the heart were similar by both techniques, but the values of V 10 and V 5 by the RapidArc planning were significantly higher (by 18% and 50%, respectively). The V 5 of the contralateral breast and lung by the RapidArc planning were

Effectiveness of respiratory-gated radiotherapy with audio-visual biofeedback for synchrotron-based scanned heavy-ion beam delivery

Science.gov (United States)

He, Pengbo; Li, Qiang; Zhao, Ting; Liu, Xinguo; Dai, Zhongying; Ma, Yuanyuan

2016-12-01

A synchrotron-based heavy-ion accelerator operates in pulse mode at a low repetition rate that is comparable to a patient’s breathing rate. To overcome inefficiencies and interplay effects between the residual motion of the target and the scanned heavy-ion beam delivery process for conventional free breathing (FB)-based gating therapy, a novel respiratory guidance method was developed to help patients synchronize their breathing patterns with the synchrotron excitation patterns by performing short breath holds with the aid of personalized audio-visual biofeedback (BFB) system. The purpose of this study was to evaluate the treatment precision, efficiency and reproducibility of the respiratory guidance method in scanned heavy-ion beam delivery mode. Using 96 breathing traces from eight healthy volunteers who were asked to breathe freely and guided to perform short breath holds with the aid of BFB, a series of dedicated four-dimensional dose calculations (4DDC) were performed on a geometric model which was developed assuming a linear relationship between external surrogate and internal tumor motions. The outcome of the 4DDCs was quantified in terms of the treatment time, dose-volume histograms (DVH) and dose homogeneity index. Our results show that with the respiratory guidance method the treatment efficiency increased by a factor of 2.23-3.94 compared with FB gating, depending on the duty cycle settings. The magnitude of dose inhomogeneity for the respiratory guidance methods was 7.5 times less than that of the non-gated irradiation, and good reproducibility of breathing guidance among different fractions was achieved. Thus, our study indicates that the respiratory guidance method not only improved the overall treatment efficiency of respiratory-gated scanned heavy-ion beam delivery, but also had the advantages of lower dose uncertainty and better reproducibility among fractions.

Keyhole behavior and liquid flow in molten pool during laser-arc hybrid welding

Science.gov (United States)

Naito, Yasuaki; Katayama, Seiji; Matsunawa, Akira

2003-03-01

Hybrid welding was carried out on Type 304 stainless steel plate under various conditions using YAG laser combined with TIG arc. During arc and laser-arc hybrid welding, arc voltage variation was measured, and arc plasma, laser-induced plume and evaporation spots as well as keyhole behavior and liquid flow in the molten pool were observed through CCD camera and X-ray real-time transmission apparatus. It was consequently found that hybrid welding possessed many features in comparison with YAG laser welding. The deepest weld bead could be produced when the YAG laser beam of high power density was shot on the molten pool made beforehand stably with TIG arc. A keyhole was long and narrow, and its behavior was rather stable inside the molten pool. It was also confirmed that porosity was reduced by the suppression of bubble formation in hybrid welding utilizing a laser of a moderate power density.

Effect of Intrafraction Prostate Motion on Proton Pencil Beam Scanning Delivery: A Quantitative Assessment

Energy Technology Data Exchange (ETDEWEB)

Tang, Shikui, E-mail: TangS@uphs.upenn.edu [Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania (United States); Deville, Curtiland; McDonough, James; Tochner, Zelig [Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania (United States); Wang, Ken Kang-Hsin [Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania (United States); Department of Radiation Oncology and Molecular Radiation Sciences, The Johns Hopkins University, Baltimore, Maryland (United States); Vapiwala, Neha; Both, Stefan [Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania (United States)

2013-10-01

Purpose: To assess the dosimetric impact caused by the interplay between intrafraction prostate motion and the intermittent delivery of proton pencil beam scanning (PBS). Methods and Materials: A cohort of 10 prostate patients was treated with PBS using a bilateral single-field uniform dose (SFUD) modality. Bilateral intensity-modulated proton therapy (IMPT) plans were generated for comparison. Because beam-on time in PBS was intermittent, the actual beam-on time was determined from treatment logs. Prostate motion was generalized according to real-time Calypso tracking data from our previously reported prospective photon trial. We investigated potential dose deviations by considering the interplay effect resulting from the worst-case scenario motion and the PBS delivery sequence. Results: For both bilateral-field SFUD and IMPT plans, clinical target volume (CTV) D{sub 99}% coverage was degraded <2% owing to prostate intrafraction motion when averaged over the course of treatment, but was >10% for the worst fraction. The standard deviation of CTV D{sub 99}% distribution was approximately 1.2%. The CTV coverage of individual fields in SFUD plans degraded as time elapsed after the initial alignment, owing to prostate drift. Intensity-modulated proton therapy and SFUD demonstrated comparable results when bilateral opposed fields were used. Single-field SFUD plans that were repainted twice, which could reduce half of the treatment time, resulted in similar CTV coverage as bilateral-field plans. Conclusions: Intrafraction prostate motion affects the actual delivered dose to CTV; however, when averaged over the course of treatment, CTV D{sub 99}% coverage degraded only approximately 2% even for the worst-case scenario. The IMPT plan results are comparable to those of the SFUD plan, and similar coverage can be achieved if treated by SFUD 1 lateral field per day when rescanning the field twice to shorten the treatment time and mitigate intrafraction motion.

The dosimetric impact of inversely optimized arc radiotherapy plan modulation for real-time dynamic MLC tracking delivery

DEFF Research Database (Denmark)

Falk, Marianne; Larsson, Tobias; Keall, P.

2012-01-01

Purpose: Real-time dynamic multileaf collimator (MLC) tracking for management of intrafraction tumor motion can be challenging for highly modulated beams, as the leaves need to travel far to adjust for target motion perpendicular to the leaf travel direction. The plan modulation can be reduced......-to-peak displacement of 2 cm and a cycle time of 6 s. The delivery was adjusted to the target motion using MLC tracking, guided in real-time by an infrared optical system. The dosimetric results were evaluated using gamma index evaluation with static target measurements as reference. Results: The plan quality...

Electrochemical Testing of Gas Tungsten Arc Welded and Reduced Pressure Electron Beam Welded Alloy 22

International Nuclear Information System (INIS)

Day, S D; Wong, F G; Gordon, S R; Wong, L L; Rebak, R B

2006-01-01

Alloy 22 (N06022) is the material selected for the fabrication of the outer shell of the nuclear waste containers for the Yucca Mountain high-level nuclear waste repository site. A key technical issue in the waste package program has been the integrity of the container weld joints. The currently selected welding process for fabricating and sealing the containers is the traditional gas tungsten arc welding (GTAW) or TIG method. An appealing faster alternative technique is reduced pressure electron beam (RPEB) welding. It was of interest to compare the corrosion properties of specimens prepared using both types of welding techniques. Standard electrochemical tests were carried on GTAW and RPEB welds as well as on base metal (non-welded) to determine their relative corrosion behavior in simulated concentrated water (SCW) at 90 C (alkaline), 1 M HCl at 60 C (acidic) and 1 M NaCl at 90 C (neutral) solutions. Results show that for all practical purposes, the three tested materials had the same electrochemical behavior in the three tested electrolytes

Electrochemical Testing of Gas Tungsten ARC Welded and Reduced Pressure Electron Beam Welded Alloy 22

International Nuclear Information System (INIS)

S. Daniel Day; Frank M.G. Wong; Steven R. Gordon; Lana L. Wong; Raul B. Rebak

2006-01-01

Alloy 22 (N06022) is the material selected for the fabrication of the outer shell of the nuclear waste containers for the Yucca Mountain high-level nuclear waste repository site. A key technical issue in the waste package program has been the integrity of the container weld joints. The currently selected welding process for fabricating and sealing the containers is the traditional gas tungsten arc welding (GTAW) or TIC method. An appealing faster alternative technique is reduced pressure electron beam (RPEB) welding. It was of interest to compare the corrosion properties of specimens prepared using both types of welding techniques. Standard electrochemical tests were carried on GTAW and RPEB welds as well as on base metal (non-welded) to determine their relative corrosion behavior in simulated concentrated water (SCW) at 90 C (alkaline), 1 M HCI at 60 C (acidic) and 1 M NaCl at 90 C (neutral) solutions. Results show that for all practical purposes, the three tested materials had the same electrochemical behavior in the three tested electrolytes

Welding of Thin Steel Plates by Hybrid Welding Process Combined TIG Arc with YAG Laser

Science.gov (United States)

Kim, Taewon; Suga, Yasuo; Koike, Takashi

TIG arc welding and laser welding are used widely in the world. However, these welding processes have some advantages and problems respectively. In order to improve problems and make use of advantages of the arc welding and the laser welding processes, hybrid welding process combined the TIG arc with the YAG laser was studied. Especially, the suitable welding conditions for thin steel plate welding were investigated to obtain sound weld with beautiful surface and back beads but without weld defects. As a result, it was confirmed that the shot position of the laser beam is very important to obtain sound welds in hybrid welding. Therefore, a new intelligent system to monitor the welding area using vision sensor is constructed. Furthermore, control system to shot the laser beam to a selected position in molten pool, which is formed by TIG arc, is constructed. As a result of welding experiments using these systems, it is confirmed that the hybrid welding process and the control system are effective on the stable welding of thin stainless steel plates.

TH-EF-BRB-06: Implementation of a Modulated-Arc Total Body Irradiation (TBI) Technique Using the RayStation Treatment Planning System

Energy Technology Data Exchange (ETDEWEB)

Phillips, J; Cheung, J; Held, M; Han, D; Morin, O [UCSF, San Francisco, CA (United States)

2016-06-15

Purpose: To develop a clinical workflow for delivering a modulated-arc total body irradiation (TBI) with RayStation scripting. This technique uses arc fields with the patient lying at floor level on a padded table and is validated through measurements taken on a custom-made TBI phantom. Methods: Treatment planning was performed for a retrospective cohort of eight patients with a diverse range of heights and body types. Each was replanned using an open-field dual arc method, with the patient in supine and prone positions on the floor of the vault. All plans were optimized using Raystation Planning 4.7.2.5 (RaySearch Laboratories, Stockholm, Sweden), with 200 cGy prescribed to the 95% of the body contour − 5mm. This results in an open-field beam that sweeps craniocaudally across the length of the patient. The technique is validated with measurements at 10 cm intervals in a custom-milled, 5 cm thick acrylic phantom. A centrally located CC13 ion chamber and a Mobile MOSFET (Best Medical Canada, Ottawa, ON) detector array were used to measure dose. Supine and prone arcs for each patient were consecutively delivered, and the aggregate dose at each point was compared to the planned dose calculated in the phantom. Results: The ion chamber measurements differed from the planned dose by an average of .5%, with a standard deviation of 2.1%. All measured data for the MOSFETS were within 10% of the corresponding planned dose except for two outlying points. The standard deviation of dose differences across the entire cohort was 4.0%. Most significant discrepancies occurred either in inhomogeneous regions with large gradients, or at inferior points where beam angle was steepest. Conclusion: We have confirmed that the planned dose is well matched to our measurements within 10% for this method of planning and delivery. We are currently incorporating this technique into our clinical workflow. This work is supported by RaySearch.

Multi-bunch effect of resistive wall in the Beam Delivery System of the Compact Linear Collider

CERN Document Server

Mutzner, R; Rumolo, G; Tomas, R; Pieloni, T

2010-01-01

Wake fields in the CLIC Beam Delivery System (BDS) can cause severe single or multi-bunch effects leading to luminosity loss. The main contributors in the BDS are geometric and resistive wall wake fields of the collimators and resistive wall wakes of the beam pipe. The present work focuses only on the multi-bunch effects from resistive wall. Using particle tracking with wake fields through the BDS, we have established the aperture radius, above which the effect of the wake fields becomes negligible. Our simulations were later extended to include a realistic aperture model along the BDS as well as the collimators. The two cases of 3 TeV and 500 GeV have been examined.

Is volumetric modulated arc therapy with constant dose rate a valid option in radiation therapy for head and neck cancer patients?

Science.gov (United States)

Didona, Annamaria; Lancellotta, Valentina; Zucchetti, Claudio; Panizza, Bianca Moira; Frattegiani, Alessandro; Iacco, Martina; Di Pilato, Anna Concetta; Saldi, Simonetta; Aristei, Cynthia

2018-01-01

Intensity-modulated radiotherapy (IMRT) improves dose distribution in head and neck (HN) radiation therapy. Volumetric-modulated arc therapy (VMAT), a new form of IMRT, delivers radiation in single or multiple arcs, varying dose rates (VDR-VMAT) and gantry speeds, has gained considerable attention. Constant dose rate VMAT (CDR-VMAT) associated with a fixed gantry speed does not require a dedicated linear accelerator like VDR-VMAT. The present study explored the feasibility, efficiency and delivery accuracy of CDR-VMAT, by comparing it with IMRT and VDR-VMAT in treatment planning for HN cancer. Step and shoot IMRT (SS-IMRT), CDR-VMAT and VDR-VMAT plans were created for 15 HN cancer patients and were generated by Pinnacle 3 TPS (v 9.8) using 6 MV photon energy. Three PTVs were defined to receive respectively prescribed doses of 66 Gy, 60 Gy and 54 Gy, in 30 fractions. Organs at risk (OARs) included the mandible, spinal cord, brain stem, parotids, salivary glands, esophagus, larynx and thyroid. SS-IMRT plans were based on 7 co-planar beams at fixed gantry angles. CDR-VMAT and VDR-VMAT plans, generated by the SmartArc module, used a 2-arc technique: one clockwise from 182° to 178° and the other one anti-clockwise from 178° to 182°. Comparison parameters included dose distribution to PTVs ( D mean , D 2% , D 50% , D 95% , D 98% and Homogeneity Index), maximum or mean doses to OARs, specific dose-volume data, the monitor units and treatment delivery times. Compared with SS-IMRT, CDR-VMAT significantly reduced the maximum doses to PTV1 and PTV2 and significantly improved all PTV3 parameters, except D 98% and D 95% . It significantly spared parotid and submandibular glands and was associated with a lower D mean to the larynx. Compared with VDR-VMAT, CDR-VMAT was linked to a significantly better D mean , to the PTV3 but results were worse for the parotids, left submandibular gland, esophagus and mandible. Furthermore, the D mean to the larynx was also worse

Whole abdomen radiation therapy in ovarian cancers: a comparison between fixed beam and volumetric arc based intensity modulation

International Nuclear Information System (INIS)

Mahantshetty, Umesh; Shrivastava, Shyamkishore; Cozzi, Luca; Jamema, Swamidas; Engineer, Reena; Deshpande, Deepak; Sarin, Rajiv; Fogliata, Antonella; Nicolini, Giorgia; Clivio, Alessandro; Vanetti, Eugenio

2010-01-01

A study was performed to assess dosimetric characteristics of volumetric modulated arcs (RapidArc, RA) and fixed field intensity modulated therapy (IMRT) for Whole Abdomen Radiotherapy (WAR) after ovarian cancer. Plans for IMRT and RA were optimised for 5 patients prescribing 25 Gy to the whole abdomen (PTV-WAR) and 45 Gy to the pelvis and pelvic nodes (PTV-Pelvis) with Simultaneous Integrated Boost (SIB) technique. Plans were investigated for 6 MV (RA6, IMRT6) and 15 MV (RA15, IMRT15) photons. Objectives were: for both PTVs V 90% > 95%, for PTV-Pelvis: D max < 105%; for organs at risk, maximal sparing was required. The MU and delivery time measured treatment efficiency. Pre-treatment Quality assurance was scored with Gamma Agreement Index (GAI) with 3% and 3 mm thresholds. IMRT and RapidArc resulted comparable for target coverage. For PTV-WAR, V 90% was 99.8 ± 0.2% and 93.4 ± 7.3% for IMRT6 and IMRT15, and 98.4 ± 1.7 and 98.6 ± 0.9% for RA6 and RA15. Target coverage resulted improved for PTV-Pelvis. Dose homogeneity resulted slightly improved by RA (Uniformity was defined as U 5-95% = D 5% -D 95% /D mean ). U 5 - 95% for PTV-WAR was 0.34 ± 0.05 and 0.32 ± 0.06 (IMRT6 and IMRT15), 0.30 ± 0.03 and 0.26 ± 0.04 (RA6 and RA15); for PTV-Pelvis, it resulted equal to 0.1 for all techniques. For organs at risk, small differences were observed between the techniques. MU resulted 3130 ± 221 (IMRT6), 2841 ± 318 (IMRT15), 538 ± 29 (RA6), 635 ± 139 (RA15); the average measured treatment time was 18.0 ± 0.8 and 17.4 ± 2.2 minutes (IMRT6 and IMRT15) and 4.8 ± 0.2 (RA6 and RA15). GAI IMRT6 = 97.3 ± 2.6%, GAI IMRT15 = 94.4 ± 2.1%, GAI RA6 = 98.7 ± 1.0% and GAI RA15 = 95.7 ± 3.7%. RapidArc showed to be a solution to WAR treatments offering good dosimetric features with significant logistic improvements compared to IMRT

Intense pulsed heavy ion beam technology

International Nuclear Information System (INIS)

Masugata, Katsumi; Ito, Hiroaki

2010-01-01

Development of intense pulsed heavy ion beam accelerator technology is described for the application of materials processing. Gas puff plasma gun and vacuum arc discharge plasma gun were developed as an active ion source for magnetically insulated pulsed ion diode. Source plasma of nitrogen and aluminum were successfully produced with the gas puff plasma gun and the vacuum arc plasma gun, respectively. The ion diode was successfully operated with gas puff plasma gun at diode voltage 190 kV, diode current 2.2 kA and nitrogen ion beam of ion current density 27 A/cm 2 was obtained. The ion composition was evaluated by a Thomson parabola spectrometer and the purity of the nitrogen ion beam was estimated to be 86%. The diode also operated with aluminum ion source of vacuum arc plasma gun. The ion diode was operated at 200 kV, 12 kA, and aluminum ion beam of current density 230 A/cm 2 was obtained. The beam consists of aluminum ions (Al (1-3)+ ) of energy 60-400 keV, and protons (90-130 keV), and the purity was estimated to be 89%. The development of the bipolar pulse accelerator (BPA) was reported. A double coaxial type bipolar pulse generator was developed as the power supply of the BPA. The generator was tested with dummy load of 7.5 ohm, bipolar pulses of -138 kV, 72 ns (1st pulse) and +130 kV, 70 ns (2nd pulse) were successively generated. By applying the bipolar pulse to the drift tube of the BPA, nitrogen ion beam of 2 A/cm 2 was observed in the cathode, which suggests the bipolar pulse acceleration. (author)

The effects of betatron phase advances on beam-beam and its compensation in RHIC

Energy Technology Data Exchange (ETDEWEB)

Luo, Y.; Fischer, W.; Gu, X.; Tepikian, S.; Trbojevic, D.

2011-03-28

In this article we perform simulation studies to investigate the effects of betatron phase advances between the beam-beam interaction points on half-integer resonance driving term, second order chromaticty and dynamic aperture in RHIC. The betatron phase advances are adjusted with artificial matrices inserted in the middle of arcs. The lattices for the 2011 RHIC polarized proton (p-p) run and 2010 RHIC Au-Au runs are used in this study. We also scan the betatron phase advances between IP8 and the electron lens for the proposed Blue ring lattice with head-on beam-beam compensation.

Respiratory gated beam delivery cannot facilitate margin reduction, unless combined with respiratory correlated image guidance

DEFF Research Database (Denmark)

Korreman, S.S.; Boyer, A.L.; Juhler-Nøttrup, Trine

2008-01-01

PURPOSE/OBJECTIVE: In radiotherapy of targets moving with respiration, beam gating is offered as a means of reducing the target motion. The purpose of this study is to evaluate the safe magnitude of margin reduction for respiratory gated beam delivery. MATERIALS/METHODS: The study is based on data...... for 17 lung cancer patients in separate protocols at Rigshospitalet and Stanford Cancer Center. Respiratory curves for external optical markers and implanted fiducials were collected using equipment based on the RPM system (Varian Medical Systems). A total of 861 respiratory curves represented external...... measurements over 30 fraction treatment courses for 10 patients, and synchronous external/internal measurements in single sessions for seven patients. Variations in respiratory amplitude (simulated coaching) and external/internal phase shifts were simulated by perturbation with realistic values. Variations...

Comparative analysis of volumetric-modulated arc therapy and intensity-modulated radiotherapy for base of tongue cancer

International Nuclear Information System (INIS)

Nithya, L.; Arulraj, Kumar; Rathinamuthu, Sasikumar; Pandey, Manish Bhushan; Nambi Raj, N. Arunai

2014-01-01

The aim of this study was to compare the various dosimetric parameters of dynamic multileaf collimator (MLC) intensity modulated radiation therapy (IMRT) plans with volumetric modulated arc therapy (VMAT) plans for base of tongue cases. All plans were done in Monaco planning system for Elekta synergy linear accelerator with 80 MLC. IMRT plans were planned with nine stationary beams, and VMAT plans were done for 360° arc with single arc or dual arc. The dose to the planning target volumes (PTV) for 70, 63, and 56 Gy was compared. The dose to 95, 98, and 50% volume of PTV were analyzed. The homogeneity index (HI) and the conformity index (CI) of the PTV 70 were also analyzed. IMRT and VMAT plan showed similar dose coverage, HI, and CI. Maximum dose and dose to 1-cc volume of spinal cord, planning risk volume (PRV) cord, and brain stem were compared. IMRT plan and VMAT plan showed similar results except for the 1 cc of PRV cord that received slightly higher dose in VMAT plan. Mean dose and dose to 50% volume of right and left parotid glands were analyzed. VMAT plan gave better sparing of parotid glands than IMRT. In normal tissue dose analyses VMAT was better than IMRT. The number of monitor units (MU) required for delivering the good quality of the plan and the time required to deliver the plan for IMRT and VMAT were compared. The number of MUs for VMAT was higher than that of IMRT plans. However, the delivery time was reduced by a factor of two for VMAT compared with IMRT. VMAT plans yielded good quality of the plan compared with IMRT, resulting in reduced treatment time and improved efficiency for base of tongue cases. (author)

Comparative analysis of volumetric-modulated arc therapy and intensity-modulated radiotherapy for base of tongue cancer

Directory of Open Access Journals (Sweden)

L Nithya

2014-01-01

Full Text Available The aim of this study was to compare the various dosimetric parameters of dynamic multileaf collimator (MLC intensity modulated radiation therapy (IMRT plans with volumetric modulated arc therapy (VMAT plans for base of tongue cases. All plans were done in Monaco planning system for Elekta synergy linear accelerator with 80 MLC. IMRT plans were planned with nine stationary beams, and VMAT plans were done for 360° arc with single arc or dual arc. The dose to the planning target volumes (PTV for 70, 63, and 56 Gy was compared. The dose to 95, 98, and 50% volume of PTV were analyzed. The homogeneity index (HI and the conformity index (CI of the PTV 70 were also analyzed. IMRT and VMAT plan showed similar dose coverage, HI, and CI. Maximum dose and dose to 1-cc volume of spinal cord, planning risk volume (PRV cord, and brain stem were compared. IMRT plan and VMAT plan showed similar results except for the 1 cc of PRV cord that received slightly higher dose in VMAT plan. Mean dose and dose to 50% volume of right and left parotid glands were analyzed. VMAT plan gave better sparing of parotid glands than IMRT. In normal tissue dose analyses VMAT was better than IMRT. The number of monitor units (MU required for delivering the good quality of the plan and the time required to deliver the plan for IMRT and VMAT were compared. The number of MUs for VMAT was higher than that of IMRT plans. However, the delivery time was reduced by a factor of two for VMAT compared with IMRT. VMAT plans yielded good quality of the plan compared with IMRT, resulting in reduced treatment time and improved efficiency for base of tongue cases.

SU-E-T-110: An Investigation On Monitor Unit Threshold and Effects On IMPT Delivery in Proton Pencil Beam Planning System

International Nuclear Information System (INIS)

Syh, J; Ding, X; Syh, J; Patel, B; Rosen, L; Wu, H

2015-01-01

Purpose: An approved proton pencil beam scanning (PBS) treatment plan might not be able to deliver because of existed extremely low monitor unit per beam spot. A dual hybrid plan with higher efficiency of higher spot monitor unit and the efficacy of less number of energy layers were searched and optimized. The range of monitor unit threshold setting was investigated and the plan quality was evaluated by target dose conformity. Methods: Certain limitations and requirements need to be checks and tested before a nominal proton PBS treatment plan can be delivered. The plan needs to be met the machine characterization, specification in record and verification to deliver the beams. Minimal threshold of monitor unit, e.g. 0.02, per spot was set to filter the low counts and plan was re-computed. Further MU threshold increment was tested in sequence without sacrificing the plan quality. The number of energy layer was also alternated due to elimination of low count layer(s). Results: Minimal MU/spot threshold, spot spacing in each energy layer and total number of energy layer and the MU weighting of beam spots of each beam were evaluated. Plan optimization between increases of the spot MU (efficiency) and less energy layers of delivery (efficacy) was adjusted. 5% weighting limit of total monitor unit per beam was feasible. Scarce spreading of beam spots was not discouraging as long as target dose conformity within 3% criteria. Conclusion: Each spot size is equivalent to the relative dose in the beam delivery system. The energy layer is associated with the depth of the targeting tumor. Our work is crucial to maintain the best possible quality plan. To keep integrity of all intrinsic elements such as spot size, spot number, layer number and the carried weighting of spots in each layer is important in this study

SU-G-BRC-10: Feasibility of a Web-Based Monte Carlo Simulation Tool for Dynamic Electron Arc Radiotherapy (DEAR)

International Nuclear Information System (INIS)

Rodrigues, A; Wu, Q; Sawkey, D

2016-01-01

Purpose: DEAR is a radiation therapy technique utilizing synchronized motion of gantry and couch during delivery to optimize dose distribution homogeneity and penumbra for treatment of superficial disease. Dose calculation for DEAR is not yet supported by commercial TPSs. The purpose of this study is to demonstrate the feasibility of using a web-based Monte Carlo (MC) simulation tool (VirtuaLinac) to calculate dose distributions for a DEAR delivery. Methods: MC simulations were run through VirtuaLinac, which is based on the GEANT4 platform. VirtuaLinac utilizes detailed linac head geometry and material models, validated phase space files, and a voxelized phantom. The input was expanded to include an XML file for simulation of varying mechanical axes as a function of MU. A DEAR XML plan was generated and used in the MC simulation and delivered on a TrueBeam in Developer Mode. Radiographic film wrapped on a cylindrical phantom (12.5 cm radius) measured dose at a depth of 1.5 cm and compared to the simulation results. Results: A DEAR plan was simulated using an energy of 6 MeV and a 3×10 cm 2 cut-out in a 15×15 cm 2 applicator for a delivery of a 90° arc. The resulting data were found to provide qualitative and quantitative evidence that the simulation platform could be used as the basis for DEAR dose calculations. The resulting unwrapped 2D dose distributions agreed well in the cross-plane direction along the arc, with field sizes of 18.4 and 18.2 cm and penumbrae of 1.9 and 2.0 cm for measurements and simulations, respectively. Conclusion: Preliminary feasibility of a DEAR delivery using a web-based MC simulation platform has been demonstrated. This tool will benefit treatment planning for DEAR as a benchmark for developing other model based algorithms, allowing efficient optimization of trajectories, and quality assurance of plans without the need for extensive measurements.

SU-G-BRC-10: Feasibility of a Web-Based Monte Carlo Simulation Tool for Dynamic Electron Arc Radiotherapy (DEAR)

Energy Technology Data Exchange (ETDEWEB)

Rodrigues, A; Wu, Q [Duke University Medical Center, Durham, NC (United States); Sawkey, D [Varian Medical Systems, Palo Alto, CA (United States)

2016-06-15

Purpose: DEAR is a radiation therapy technique utilizing synchronized motion of gantry and couch during delivery to optimize dose distribution homogeneity and penumbra for treatment of superficial disease. Dose calculation for DEAR is not yet supported by commercial TPSs. The purpose of this study is to demonstrate the feasibility of using a web-based Monte Carlo (MC) simulation tool (VirtuaLinac) to calculate dose distributions for a DEAR delivery. Methods: MC simulations were run through VirtuaLinac, which is based on the GEANT4 platform. VirtuaLinac utilizes detailed linac head geometry and material models, validated phase space files, and a voxelized phantom. The input was expanded to include an XML file for simulation of varying mechanical axes as a function of MU. A DEAR XML plan was generated and used in the MC simulation and delivered on a TrueBeam in Developer Mode. Radiographic film wrapped on a cylindrical phantom (12.5 cm radius) measured dose at a depth of 1.5 cm and compared to the simulation results. Results: A DEAR plan was simulated using an energy of 6 MeV and a 3×10 cm{sup 2} cut-out in a 15×15 cm{sup 2} applicator for a delivery of a 90° arc. The resulting data were found to provide qualitative and quantitative evidence that the simulation platform could be used as the basis for DEAR dose calculations. The resulting unwrapped 2D dose distributions agreed well in the cross-plane direction along the arc, with field sizes of 18.4 and 18.2 cm and penumbrae of 1.9 and 2.0 cm for measurements and simulations, respectively. Conclusion: Preliminary feasibility of a DEAR delivery using a web-based MC simulation platform has been demonstrated. This tool will benefit treatment planning for DEAR as a benchmark for developing other model based algorithms, allowing efficient optimization of trajectories, and quality assurance of plans without the need for extensive measurements.

Early clinical experience of radiotherapy of prostate cancer with volumetric modulated arc therapy

Directory of Open Access Journals (Sweden)

Valli Mariacarla

2010-06-01

Full Text Available Abstract Background To report about initial clinical experience in radiation treatment of carcinoma of prostate with volumetric modulated arcs with the RapidArc (RA technology. Methods Forty-five patients with a median age of 72 ± 3, affected by prostate carcinoma (T1c: 22 patients, T2a-b: 17 patients, T3a-b: 6 patients. N0: 43 patients, N1-Nx: 2 patients, all M0, with initial PSA of 10.0 ± 3.0 ng/mL, were treated with RapidArc in a feasibility study. All patients were treated with single arc using 6MV photons. Dose prescription ranged between 76 (7 patients and 78 Gy (38 patients in 2Gy/fraction. Plan quality was assessed by means of Dose Volume Histogram (DVH analysis. Technical parameters of arcs and pre-treatment quality assurance results (Gamma Agreement Index, GAI are reported to describe delivery features. Early toxicity was scored (according to the Common Terminology Criteria of Adverse Effects scale, CTCAE, scale at the end of treatment together with biochemical outcome (PSA. Results From DVH data, target coverage was fulfilling planning objectives: V95% was in average higher than 98% and V107%~0.0% (D2%~104.0% in average. Homogeneity D5%-D95% ranged between 6.2 ± 1.0% to 6.7 ± 1.3%. For rectum, all planning objectives were largely met (e.g. V70Gy = 10.7 ± 5.5% against an objective of 2% = 79.4 ± 1.2Gy against an objective of 80.0Gy. Maximum dose to femurs was D2% = 36.7 ± 5.4Gy against an objective of 47Gy. Monitor Units resulted: MU/Gy = 239 ± 37. Average beam on time was 1.24 ± 0.0 minutes. Pre-treatment GAI resulted in 98.1 ± 1.1%. Clinical data were recorded as PSA at 6 weeks after RT, with median values of 0.4 ± 0.4 ng/mL. Concerning acute toxicity, no patient showed grade 2-3 rectal toxicity; 5/42 (12% patients experienced grade 2 dysuria; 18/41 (44% patients preserved complete or partial erectile function. Conclusion RapidArc proved to be a safe, qualitative and advantageous treatment modality for prostate cancer.

The ARCS radial collimator

International Nuclear Information System (INIS)

Stone, M.B.; Abernathy, D.L.; Niedziela, J.L.; Overbay, M.A.

2015-01-01

We have designed, installed, and commissioned a scattered beam radial collimator for use at the ARCS Wide Angular Range Chopper Spectrometer at the Spallation Neutron Source. The collimator has been designed to work effectively for thermal and epithermal neutrons and with a range of sample environments. Other design considerations include the accommodation of working within a high vacuum environment and having the ability to quickly install and remove the collimator from the scattered beam. The collimator is composed of collimating blades (or septa). The septa are 12 micron thick Kapton foils coated on each side with 39 microns of enriched boron carbide ( 10 B 4 C with 10 B > 96%) in an ultra-high vacuum compatible binder. The collimator blades represent an additional 22 m 2 of surface area. In the article we present collimator's design and performance and methodologies for its effective use

Multi-Bunch effect of resistive wall in the beam delivery system of the Compact Linear Collider

CERN Document Server

Mutzner, Raphael; Pieloni, Tatiana; Rivkin, Leonid

2010-01-01

Wake fields in the CLIC Beam Delivery System (BDS) can cause severe single or multi-bunch effects leading to luminosity loss. The main contributors in the BDS are geometric and resistive wall wake fields of the collimators and resistive wall wakes of the beam pipe. The present master thesis focuses only on the multi-bunch effects from resistive wall. Using particle tracking with wake fields through the BDS, we have established the aperture radius, above which the effect of the wake fields becomes negligible. Simulations were later extended to include a realistic aperture model along the BDS as well as the collimators. We examine the two cases of 3 TeV and 500 GeV in this work, for stainless steel and copper pipes.

A test facility for the international linear collider at SLAC end station a for prototypes of beam delivery and IR components

International Nuclear Information System (INIS)

Hildreth, M.D.; Erickson, R.; Frisch, J.

2006-01-01

The SLAC Linac can deliver damped bunches with ILC parameters for bunch charge and bunch length to End Station A. A 10Hz beam at 28.5 GeV energy can be delivered there, parasitic with PEP-II operation. We plan to use this facility to test prototype components of the Beam Delivery System and Interaction Region. We discuss our plans for this ILC Test Facility and preparations for carrying out experiments related to collimator wakefields and energy spectrometers. We also plan an interaction region mockup to investigate effects from backgrounds and beam-induced electromagnetic interference. (author)

A synchronous beam sweeper for heavy ions

International Nuclear Information System (INIS)

Bogaty, J.M.

1989-01-01

The Argonne Tandem Linac Accelerator System (ATLAS) facility at Argonne National Laboratory provides a wide range of accelerated heavy ions from the periodic table. Frequently, the beam delivery rate of 12 MHz is too fast for the type of experiment on line. Reaction by-products from a target bombardment may have a decay interval much longer than the dead time between beam bunches. To prevent data from being corrupted by incoming ions a beam sweeper was developed which synchronously eliminates selected beam bunches to suit experimental needs. As the SWEEPER is broad band (DC to 6 MHz) beam delivery rates can be instantaneously changed. Ion beam bunches are selectively kicked out by an electrostatic dipole electrode pulsed to 2 kVDC. The system has been used for almost three years with several hundred hours of operating time logged to date. Beam bunch delivery rates of 6 MHz down to 25 kHz have been provided. Since this is a non-resonant system any beam delivery rate from 6 MHz down to zero can be set. In addition, burst modes have been used where beam is supplied in 12 MHz bursts and then shut down for a period of time set by the user. 3 figs

Single Pass Collider Memo: Gradient Perturbations of the SLC arc

Energy Technology Data Exchange (ETDEWEB)

Weng, W.T.; Sands, M.; /SLAC

2016-12-16

As the beam passes through the arcs, the gradient it encounters at each magnet differs from the design value. This deviation may be in part random and in part systematic. In this note we make estimates of the effects to be expected from both kinds of errors.

Interplay effects in proton scanning for lung: a 4D Monte Carlo study assessing the impact of tumor and beam delivery parameters

International Nuclear Information System (INIS)

Dowdell, S; Grassberger, C; Sharp, G C; Paganetti, H

2013-01-01

Relative motion between a tumor and a scanning proton beam results in a degradation of the dose distribution (interplay effect). This study investigates the relationship between beam scanning parameters and the interplay effect, with the goal of finding parameters that minimize interplay. 4D Monte Carlo simulations of pencil beam scanning proton therapy treatments were performed using the 4DCT geometry of five lung cancer patients of varying tumor size (50.4–167.1 cc) and motion amplitude (2.9–30.1 mm). Treatments were planned assuming delivery in 35 × 2.5 Gy(RBE) fractions. The spot size, time to change the beam energy (τ es ), time required for magnet settling (τ ss ), initial breathing phase, spot spacing, scanning direction, scanning speed, beam current and patient breathing period were varied for each of the five patients. Simulations were performed for a single fraction and an approximation of conventional fractionation. For the patients considered, the interplay effect could not be predicted using the superior–inferior motion amplitude alone. Larger spot sizes (σ ∼ 9–16 mm) were less susceptible to interplay, giving an equivalent uniform dose (EUD) of 99.0 ± 4.4% (1 standard deviation) in a single fraction compared to 86.1 ± 13.1% for smaller spots (σ ∼ 2–4 mm). The smaller spot sizes gave EUD values as low as 65.3% of the prescription dose in a single fraction. Reducing the spot spacing improved the target dose homogeneity. The initial breathing phase can have a significant effect on the interplay, particularly for shorter delivery times. No clear benefit was evident when scanning either parallel or perpendicular to the predominant axis of motion. Longer breathing periods decreased the EUD. In general, longer delivery times led to lower interplay effects. Conventional fractionation showed significant improvement in terms of interplay, giving a EUD of at least 84.7% and 100.0% of the prescription dose for the small and larger spot sizes

Interplay effects in proton scanning for lung: a 4D Monte Carlo study assessing the impact of tumor and beam delivery parameters.

Science.gov (United States)

Dowdell, S; Grassberger, C; Sharp, G C; Paganetti, H

2013-06-21

Relative motion between a tumor and a scanning proton beam results in a degradation of the dose distribution (interplay effect). This study investigates the relationship between beam scanning parameters and the interplay effect, with the goal of finding parameters that minimize interplay. 4D Monte Carlo simulations of pencil beam scanning proton therapy treatments were performed using the 4DCT geometry of five lung cancer patients of varying tumor size (50.4-167.1 cc) and motion amplitude (2.9-30.1 mm). Treatments were planned assuming delivery in 35 × 2.5 Gy(RBE) fractions. The spot size, time to change the beam energy (τes), time required for magnet settling (τss), initial breathing phase, spot spacing, scanning direction, scanning speed, beam current and patient breathing period were varied for each of the five patients. Simulations were performed for a single fraction and an approximation of conventional fractionation. For the patients considered, the interplay effect could not be predicted using the superior-inferior motion amplitude alone. Larger spot sizes (σ ~ 9-16 mm) were less susceptible to interplay, giving an equivalent uniform dose (EUD) of 99.0 ± 4.4% (1 standard deviation) in a single fraction compared to 86.1 ± 13.1% for smaller spots (σ ~ 2-4 mm). The smaller spot sizes gave EUD values as low as 65.3% of the prescription dose in a single fraction. Reducing the spot spacing improved the target dose homogeneity. The initial breathing phase can have a significant effect on the interplay, particularly for shorter delivery times. No clear benefit was evident when scanning either parallel or perpendicular to the predominant axis of motion. Longer breathing periods decreased the EUD. In general, longer delivery times led to lower interplay effects. Conventional fractionation showed significant improvement in terms of interplay, giving a EUD of at least 84.7% and 100.0% of the prescription dose for the small and larger spot sizes respectively. The

Recent advances in high current vacuum arc ion sources for heavy ion fusion

CERN Document Server

Qi Nian Sheng; Prasad, R R; Krishnan, M S; Anders, A; Kwan, J; Brown, I

2001-01-01

For a heavy ion fusion induction linac driver, a source of heavy ions with charge states 1+-3+, approx 0.5 A current beams, approx 20 mu s pulse widths and approx 10 Hz repetition rates is required. Thermionic sources have been the workhorse for the Heavy Ion Fusion (HIF) program to date, but suffer from heating problems for large areas and contamination. They are limited to low (contact) ionization potential elements and offer relatively low ion fluxes with a charge state limited to 1+. Gas injection sources suffer from partial ionization and deleterious neutral gas effects. The above shortcomings of the thermionic ion sources can be overcome by a vacuum arc ion source. The vacuum arc ion source is a good candidate for HIF applications. It is capable of providing ions of various elements and different charge states in short and long pulse bursts and high beam current density. Under a Phase-I STTR from DOE, the feasibility of the vacuum arc ion source for the HIF applications was investigated. We have modifie...

Simultaneous delivery of electron beam therapy and ultrasound hyperthermia using scanning reflectors: a feasibility study

International Nuclear Information System (INIS)

Moros, Eduardo G.; Straube, William L.; Klein, Eric E.; Yousaf, Muhammed; Myerson, Robert J.

1995-01-01

power reflectivities of 87-96% that of brass, and that for smooth surfaces the reflections from air reflectors were as specular as those from brass reflectors. Acoustic pressure fields measurements of the SURAS for two different arrays showed that the 50% pressure amplitude contours were well-distributed across the projected surface area of the array for different distances separating the array and the reflector. Finally, film dosimetry showed that the electron dose distribution was not affected by the air reflector of the SURAS either for the scanning case or the stationary case. This indicates that the reflectors as made are basically water-equivalent in terms of high energy ionizing radiation. The measured isodoses also indicate that the constructed SURAS prototype would allow the delivery of adequate radiation (90% isodose) to a depth of 2.0 cm. Conclusions: The results presented show that the SURAS design has the potential to deliver hyperthermia to large superficial tumors, while allowing simultaneous irradiation with 20 MeV electron beams without adverse effects on the radiation dose delivery

Metal halide arc discharge lamp having short arc length

Science.gov (United States)

Muzeroll, Martin E. (Inventor)

1994-01-01

A metal halide arc discharge lamp includes a sealed light-transmissive outer jacket, a light-transmissive shroud located within the outer jacket and an arc tube assembly located within the shroud. The arc tube assembly includes an arc tube, electrodes mounted within the arc tube and a fill material for supporting an arc discharge. The electrodes have a spacing such that an electric field in a range of about 60 to 95 volts per centimeter is established between the electrodes. The diameter of the arc tube and the spacing of the electrodes are selected to provide an arc having an arc diameter to arc length ratio in a range of about 1.6 to 1.8. The fill material includes mercury, sodium iodide, scandium tri-iodide and a rare gas, and may include lithium iodide. The lamp exhibits a high color rendering index, high lumen output and high color temperature.

Commissioning and first clinical application of mARC treatment

Energy Technology Data Exchange (ETDEWEB)

Dzierma, Yvonne; Nuesken, Frank G.; Kremp, Stephanie; Palm, Jan; Licht, Norbert P.; Ruebe, Christian [Universitaetsklinikum des Saarlandes, Klinik fuer Strahlentherapie und Radioonkologie, Homburg, Saarland (Germany)

2014-11-15

The modulated arc (mARC) technique has recently been introduced for Siemens ARTISTE linear accelerators. We present the first experiences with the commissioning of the system and first patient treatments. Treatment planning and delivery are presented for the Prowess Panther treatment planning system or, alternatively, an in-house code. Dosimetric verification is performed both by point dose measurements and in 3D dose distribution. Depending on the target volume, one or two arcs can be used to create highly conformal plans. Dosimetric verification of the converted mARC plans with step-and-shoot plans shows deviations below 1 % in absolute point dose; in the 3D dose distribution, over 95 % of the points pass the 3D gamma criteria (3 % deviation in local dose and 3 mm distance to agreement for doses > 20 % of the maximum). Patient specific verification of the mARC dose distribution with the calculations has a similar pass rate. Treatment times range between 2 and 5 min for a single arc. To our knowledge, this is the first report of clinical application of the mARC technique. The mARC offers the possibility to save significant amounts of time, with single-arc treatments of only a few minutes achieving comparable dose distribution to IMRT plans taking up to twice as long. (orig.) [German] Die mARC (modulated arc) Technik wurde vor kurzen fuer Siemens ARTISTE Linearbeschleuniger eingefuehrt. Wir zeigen die ersten Erfahrungen mit der Kommissionierung des Systems sowie die ersten Patientenbestrahlungen. Bestrahlungsplanung und Behandlung werden fuer das Prowess Panther Bestrahlungsplanungssystem oder alternativ in einer in-house-Loesung praesentiert. Die dosimetrische Verifikation wurde sowohl mit Punktmessungen als auch fuer die 3D-Dosisverteilung durchgefuehrt. Je nach Zielvolumen koennen mit einem oder zwei Boegen hochkonformale Plaene erzeugt werden. Die dosimetrische Verifikation konvertierter mARC-Plaene gegen step-and-shoot-Plaene weicht in absoluter Dosis um

MO-AB-BRA-01: A Global Level Set Based Formulation for Volumetric Modulated Arc Therapy

Energy Technology Data Exchange (ETDEWEB)

Nguyen, D; Lyu, Q; Ruan, D; O’Connor, D; Low, D; Sheng, K [Department of Radiation Oncology, University of California Los Angeles, Los Angeles, CA (United States)

2016-06-15

Purpose: The current clinical Volumetric Modulated Arc Therapy (VMAT) optimization is formulated as a non-convex problem and various greedy heuristics have been employed for an empirical solution, jeopardizing plan consistency and quality. We introduce a novel global direct aperture optimization method for VMAT to overcome these limitations. Methods: The global VMAT (gVMAT) planning was formulated as an optimization problem with an L2-norm fidelity term and an anisotropic total variation term. A level set function was used to describe the aperture shapes and adjacent aperture shapes were penalized to control MLC motion range. An alternating optimization strategy was implemented to solve the fluence intensity and aperture shapes simultaneously. Single arc gVMAT plans, utilizing 180 beams with 2° angular resolution, were generated for a glioblastoma multiforme (GBM), lung (LNG), and 2 head and neck cases—one with 3 PTVs (H&N3PTV) and one with 4 PTVs (H&N4PTV). The plans were compared against the clinical VMAT (cVMAT) plans utilizing two overlapping coplanar arcs. Results: The optimization of the gVMAT plans had converged within 600 iterations. gVMAT reduced the average max and mean OAR dose by 6.59% and 7.45% of the prescription dose. Reductions in max dose and mean dose were as high as 14.5 Gy in the LNG case and 15.3 Gy in the H&N3PTV case. PTV coverages (D95, D98, D99) were within 0.25% of the prescription dose. By globally considering all beams, the gVMAT optimizer allowed some beams to deliver higher intensities, yielding a dose distribution that resembles a static beam IMRT plan with beam orientation optimization. Conclusions: The novel VMAT approach allows for the search of an optimal plan in the global solution space and generates deliverable apertures directly. The single arc VMAT approach fully utilizes the digital linacs’ capability in dose rate and gantry rotation speed modulation. Varian Medical Systems, NIH grant R01CA188300, NIH grant R43CA183390.

Monitoring ARC services with GangliARC

International Nuclear Information System (INIS)

Cameron, D; Karpenko, D

2012-01-01

Monitoring of Grid services is essential to provide a smooth experience for users and provide fast and easy to understand diagnostics for administrators running the services. GangliARC makes use of the widely-used Ganglia monitoring tool to present web-based graphical metrics of the ARC computing element. These include statistics of running and finished jobs, data transfer metrics, as well as showing the availability of the computing element and hardware information such as free disk space left in the ARC cache. Ganglia presents metrics as graphs of the value of the metric over time and shows an easily-digestable summary of how the system is performing, and enables quick and easy diagnosis of common problems. This paper describes how GangliARC works and shows numerous examples of how the generated data can quickly be used by an administrator to investigate problems. It also presents possibilities of combining GangliARC with other commonly-used monitoring tools such as Nagios to easily integrate ARC monitoring into the regular monitoring infrastructure of any site or computing centre.

Simulations of the magnet misalignments, field errors and orbit correction for the SLC north arc

International Nuclear Information System (INIS)

Kheifets, S.; Chao, A.; Jaeger, J.; Shoaee, H.

1983-11-01

Given the intensity of linac bunches and their repetition rate the desired luminosity of SLC 1.0 x 10 30 cm -2 sec -1 requires focusing the interaction bunches to a spot size in the micrometer (μm) range. The lattice that achieves this goal is obtained by careful design of both the arcs and the final focus systems. For the micrometer range of the beam spot size both the second order geometric and chromatic aberrations may be completely destructive. The concept of second order achromat proved to be extremely important in this respect and the arcs are built essentially as a sequence of such achromats. Between the end of the linac and the interaction point (IP) there are three special sections in addition to the regular structure: matching section (MS) designed for matching the phase space from the linac to the arcs, reverse bend section (RB) which provides the matching when the sign of the curvature is reversed in the arc and the final focus system (FFS). The second order calculations are done by the program TURTLE. Using the TURTLE histogram in the x-y plane and assuming identical histogram for the south arc, corresponding 'luminosity' L is found. The simulation of the misalignments and error effects have to be done simultaneously with the design and simulation of the orbit correction scheme. Even after the orbit is corrected and the beam can be transmitted through the vacuum chamber, the focusing of the beam to the desired size at the IP remains a serious potential problem. It is found, as will be elaborated later, that even for the best achieved orbit correction, additional corrections of the dispersion function and possibly transfer matrix are needed. This report describes a few of the presently conceived correction schemes and summarizes some results of computer simulations done for the SLC north arc. 8 references, 12 figures, 6 tables

Arc Interference Behavior during Twin Wire Gas Metal Arc Welding Process

Directory of Open Access Journals (Sweden)

Dingjian Ye

2013-01-01

Full Text Available In order to study arc interference behavior during twin wire gas metal arc welding process, the synchronous acquisition system has been established to acquire instantaneous information of arc profile including dynamic arc length variation as well as relative voltage and current signals. The results show that after trailing arc (T-arc is added to the middle arc (M-arc in a stable welding process, the current of M arc remains unchanged while the agitation increases; the voltage of M arc has an obvious increase; the shape of M arc changes, with increasing width, length, and area; the transfer frequency of M arc droplet increases and the droplet itself becomes smaller. The wire extension length of twin arc turns out to be shorter than that of single arc welding.

Homogenized blocked arcs for multicriteria optimization of radiotherapy: Analytical and numerical solutions

International Nuclear Information System (INIS)

Fenwick, John D.; Pardo-Montero, Juan

2010-01-01

Purpose: Homogenized blocked arcs are intuitively appealing as basis functions for multicriteria optimization of rotational radiotherapy. Such arcs avoid an organ-at-risk (OAR), spread dose out well over the rest-of-body (ROB), and deliver homogeneous doses to a planning target volume (PTV) using intensity modulated fluence profiles, obtainable either from closed-form solutions or iterative numerical calculations. Here, the analytic and iterative arcs are compared. Methods: Dose-distributions have been calculated for nondivergent beams, both including and excluding scatter, beam penumbra, and attenuation effects, which are left out of the derivation of the analytic arcs. The most straightforward analytic arc is created by truncating the well-known Brahme, Roos, and Lax (BRL) solution, cutting its uniform dose region down from an annulus to a smaller nonconcave region lying beyond the OAR. However, the truncation leaves behind high dose hot-spots immediately on either side of the OAR, generated by very high BRL fluence levels just beyond the OAR. These hot-spots can be eliminated using alternative analytical solutions ''C'' and ''L,'' which, respectively, deliver constant and linearly rising fluences in the gap region between the OAR and PTV (before truncation). Results: Measured in terms of PTV dose homogeneity, ROB dose-spread, and OAR avoidance, C solutions generate better arc dose-distributions than L when scatter, penumbra, and attenuation are left out of the dose modeling. Including these factors, L becomes the best analytical solution. However, the iterative approach generates better dose-distributions than any of the analytical solutions because it can account and compensate for penumbra and scatter effects. Using the analytical solutions as starting points for the iterative methodology, dose-distributions almost as good as those obtained using the conventional iterative approach can be calculated very rapidly. Conclusions: The iterative methodology is

Image processing for the Advanced Radiographic Capability (ARC) at the National Ignition Facility

Science.gov (United States)

Leach, Richard R.; Awwal, Abdul A. S.; Lowe-Webb, Roger; Miller-Kamm, Victoria; Orth, Charles; Roberts, Randy; Wilhelmsen, Karl

2016-09-01

The Advance Radiographic Capability (ARC) at the National Ignition Facility (NIF) is a laser system that employs up to four petawatt (PW) lasers to produce a sequence of short-pulse kilo-Joule laser pulses with controllable delays that generate X-rays to provide backlighting for high-density internal confinement fusion (ICF) capsule targets. Multi-frame, hard-X-ray radiography of imploding NIF capsules is a capability which is critical to the success of NIF's missions. ARC is designed to employ up to eight backlighters with tens-of-picosecond temporal resolution, to record the dynamics and produce an X-ray "motion picture" of the compression and ignition of cryogenic deuterium-tritium targets. ARC will generate tens-of-picosecond temporal resolution during the critical phases of ICF shots. Additionally, ARC supports a variety of other high energy density experiments including fast ignition studies on NIF. The automated alignment image analysis algorithms use digital camera sensor images to direct ARC beams onto the tens-of-microns scale metal wires. This paper describes the ARC automatic alignment sequence throughout the laser chain from pulse initiation to target with an emphasis on the image processing algorithms that generate the crucial alignment positions for ARC. The image processing descriptions and flow diagrams detail the alignment control loops throughout the ARC laser chain beginning in the ARC high-contrast front end (HCAFE), on into the ARC main laser area, and ending in the ARC target area.

Effect of beam oscillation on borated stainless steel electron beam welds

Energy Technology Data Exchange (ETDEWEB)

RajaKumar, Guttikonda [Tagore Engineering College, Chennai (India). Dept. of Mechanical Engineering; Ram, G.D. Janaki [Indian Institute of Technology (IIT), Chennai (India). Dept. of Metallurgical and Materials Engineering; Rao, S.R. Koteswara [SSN College of Engineering, Chennai (India). Mechanical Engineering

2015-07-01

Borated stainless steels are used in nuclear power plants to control neutron criticality in reactors as control rods, shielding material, spent fuel storage racks and transportation casks. In this study, bead on plate welds were made using gas tungsten arc welding (GTAW) and electron beam welding (EBW) processes. Electron beam welds made using beam oscillation technique exhibited higher tensile strength values compared to that of GTA welds. Electron beam welds were found to show fine dendritic microstructure while GTA welds exhibited larger dendrites. While both processes produced defect free welds, GTA welds are marked by partially melted zone (PMZ) where the hardness is low. EBW obviate the PMZ failure due to low heat input and in case of high heat input GTA welding process failure occurs in the PMZ.

Effect of beam oscillation on borated stainless steel electron beam welds

International Nuclear Information System (INIS)

RajaKumar, Guttikonda; Ram, G.D. Janaki; Rao, S.R. Koteswara

2015-01-01

Borated stainless steels are used in nuclear power plants to control neutron criticality in reactors as control rods, shielding material, spent fuel storage racks and transportation casks. In this study, bead on plate welds were made using gas tungsten arc welding (GTAW) and electron beam welding (EBW) processes. Electron beam welds made using beam oscillation technique exhibited higher tensile strength values compared to that of GTA welds. Electron beam welds were found to show fine dendritic microstructure while GTA welds exhibited larger dendrites. While both processes produced defect free welds, GTA welds are marked by partially melted zone (PMZ) where the hardness is low. EBW obviate the PMZ failure due to low heat input and in case of high heat input GTA welding process failure occurs in the PMZ.

JEMMRLA - Electron Model of a Muon RLA with Multi-pass Arcs

Energy Technology Data Exchange (ETDEWEB)

Bogacz, Slawomir Alex; Krafft, Geoffrey A.; Morozov, Vasiliy S.; Roblin, Yves R.

2013-06-01

We propose a demonstration experiment for a new concept of a 'dogbone' RLA with multi-pass return arcs -- JEMMRLA (Jlab Electron Model of Muon RLA). Such an RLA with linear-field multi-pass arcs was introduced for rapid acceleration of muons for the next generation of Muon Facilities. It allows for efficient use of expensive RF while the multi-pass arc design based on linear combined-function magnets exhibits a number of advantages over separate-arc or pulsed-arc designs. Here we describe a test of this concept by scaling a GeV scale muon design for electrons. Scaling muon momenta by the muon-to-electron mass ratio leads to a scheme, in which a 4.5 MeV electron beam is injected in the middle of a 3 MeV/pass linac with two double-pass return arcs and is accelerated to 18 MeV in 4.5 passes. All spatial dimensions including the orbit distortion are scaled by a factor of 7.5, which arises from scaling the 200 MHz muon RF to a readily available 1.5 GHz. The hardware requirements are not very demanding making it straightforward to implement. Such an RLA may have applications going beyond muon acceleration: in medical isotope production, radiation cancer therapy and homeland security.

Arc Shape Characteristics with Ultra-High-Frequency Pulsed Arc Welding

Directory of Open Access Journals (Sweden)

Mingxuan Yang

2017-01-01

Full Text Available Arc plasma possesses a constriction phenomenon with a pulsed current. The constriction is created by the Lorentz force, the radial electromagnetic force during arc welding, which determines the energy distribution of the arc plasma. Welding experiments were carried out with ultra-high-frequency pulsed arc welding (UHFP-AW. Ultra-high-speed camera observations were produced for arc surveillance. Hue-saturation-intensity (HSI image analysis was used to distinguish the regions of the arc plasma that represented the heat energy distribution. The measurement of arc regions indicated that, with an ultra-high-frequency pulsed arc, the constriction was not only within the decreased arc geometry, but also within the constricted arc core region. This can be checked by the ratio of the core region to the total area. The arc core region expanded significantly at 40 kHz at 60 A. A current level of 80 A caused a decrease in the total region of the arc. Meanwhile, the ratio of the core region to the total increased. It can be concluded that arc constriction depends on the increased area of the core region with the pulsed current (>20 kHz.

Modification of anti-bacterial surface properties of textile polymers by vacuum arc ion source implantation

International Nuclear Information System (INIS)

Nikolaev, A.G.; Yushkov, G.Yu.; Oks, E.M.; Oztarhan, A.; Akpek, A.; Hames-Kocabas, E.; Urkac, E.S.; Brown, I.G.

2014-01-01

Highlights: • Ion implantation. • Anti-bacterial properties. • Textile polymer. • Vacuum arc ion source. - Abstract: Ion implantation provides an important technology for the modification of material surface properties. The vacuum arc ion source is a unique instrument for the generation of intense beams of metal ions as well as gaseous ions, including mixed metal–gas beams with controllable metal:gas ion ratio. Here we describe our exploratory work on the application of vacuum arc ion source-generated ion beams for ion implantation into polymer textile materials for modification of their biological cell compatibility surface properties. We have investigated two specific aspects of cell compatibility: (i) enhancement of the antibacterial characteristics (we chose to use Staphylococcus aureus bacteria) of ion implanted polymer textile fabric, and (ii) the “inverse” concern of enhancement of neural cell growth rate (we chose Rat B-35 neuroblastoma cells) on ion implanted polymer textile. The results of both investigations were positive, with implantation-generated antibacterial efficiency factor up to about 90%, fully comparable to alternative conventional (non-implantation) approaches and with some potentially important advantages over the conventional approach; and with enhancement of neural cell growth rate of up to a factor of 3.5 when grown on suitably implanted polymer textile material

Modification of anti-bacterial surface properties of textile polymers by vacuum arc ion source implantation

Energy Technology Data Exchange (ETDEWEB)

Nikolaev, A.G., E-mail: nik@opee.hcei.tsc.ru [High Current Electronics Institute, Siberian Branch of the Russian Academy of Sciences, Tomsk 634055 (Russian Federation); Yushkov, G.Yu.; Oks, E.M. [High Current Electronics Institute, Siberian Branch of the Russian Academy of Sciences, Tomsk 634055 (Russian Federation); Oztarhan, A. [Izmir University, Izmir 35140 (Turkey); Akpek, A.; Hames-Kocabas, E.; Urkac, E.S. [Bioengineering Department, Ege University, Bornova 35100, Izmir (Turkey); Brown, I.G. [Lawrence Berkeley National Laboratory, Berkeley, CA 94708 (United States)

2014-08-15

Highlights: • Ion implantation. • Anti-bacterial properties. • Textile polymer. • Vacuum arc ion source. - Abstract: Ion implantation provides an important technology for the modification of material surface properties. The vacuum arc ion source is a unique instrument for the generation of intense beams of metal ions as well as gaseous ions, including mixed metal–gas beams with controllable metal:gas ion ratio. Here we describe our exploratory work on the application of vacuum arc ion source-generated ion beams for ion implantation into polymer textile materials for modification of their biological cell compatibility surface properties. We have investigated two specific aspects of cell compatibility: (i) enhancement of the antibacterial characteristics (we chose to use Staphylococcus aureus bacteria) of ion implanted polymer textile fabric, and (ii) the “inverse” concern of enhancement of neural cell growth rate (we chose Rat B-35 neuroblastoma cells) on ion implanted polymer textile. The results of both investigations were positive, with implantation-generated antibacterial efficiency factor up to about 90%, fully comparable to alternative conventional (non-implantation) approaches and with some potentially important advantages over the conventional approach; and with enhancement of neural cell growth rate of up to a factor of 3.5 when grown on suitably implanted polymer textile material.

On the use of volumetric-modulated arc therapy for single-fraction thoracic vertebral metastases stereotactic body radiosurgery

Energy Technology Data Exchange (ETDEWEB)

Pokhrel, Damodar, E-mail: damodar.pokhrel@uky.edu; Sood, Sumit; McClinton, Christopher; Shen, Xinglei; Badkul, Rajeev; Jiang, Hongyu; Mallory, Matthew; Mitchell, Mellissa; Wang, Fen; Lominska, Christopher

2017-04-01

To retrospectively evaluate quality, efficiency, and delivery accuracy of volumetric-modulated arc therapy (VMAT) plans for single-fraction treatment of thoracic vertebral metastases using image-guided stereotactic body radiosurgery (SBRS) after RTOG 0631 dosimetric compliance criteria. After obtaining credentialing for MD Anderson spine phantom irradiation validation, 10 previously treated patients with thoracic vertebral metastases with noncoplanar hybrid arcs using 1 to 2 3D-conformal partial arcs plus 7 to 9 intensity-modulated radiation therapy beams were retrospectively re-optimized with VMAT using 3 full coplanar arcs. Tumors were located between T2 and T12. Contrast-enhanced T1/T2-weighted magnetic resonance images were coregistered with planning computed tomography and planning target volumes (PTV) were between 14.4 and 230.1 cc (median = 38.0 cc). Prescription dose was 16 Gy in 1 fraction with 6 MV beams at Novalis-TX linear accelerator consisting of micro multileaf collimators. Each plan was assessed for target coverage using conformality index, the conformation number, the ratio of the volume receiving 50% of the prescription dose over PTV, R50%, homogeneity index (HI), and PTV-1600 coverage per RTOG 0631 requirements. Organs-at-risk doses were evaluated for maximum doses to spinal cord (D{sub 0.03} {sub cc}, D{sub 0.35} {sub cc}), partial spinal cord (D{sub 10%}), esophagus (D{sub 0.03} {sub cc} and D{sub 5} {sub cc}), heart (D{sub 0.03} {sub cc} and D{sub 15} {sub cc}), and lung (V{sub 5}, V{sub 10}, and maximum dose to 1000 cc of lung). Dose delivery efficiency and accuracy of each VMAT-SBRS plan were assessed using quality assurance (QA) plan on MapCHECK device. Total beam-on time was recorded during QA procedure, and a clinical gamma index (2%/2 mm and 3%/3 mm) was used to compare agreement between planned and measured doses. All 10 VMAT-SBRS plans met RTOG 0631 dosimetric requirements for PTV coverage. The plans demonstrated highly conformal and

A novel implementation of mARC treatment for non-dedicated planning systems using converted IMRT plans

International Nuclear Information System (INIS)

Dzierma, Yvonne; Nuesken, Frank; Licht, Norbert; Ruebe, Christian

2013-01-01

The modulated arc (mARC) technique has recently been introduced by Siemens as an analogue to VMAT treatment. However, up to now only one certified treatment planning system supports mARC planning. We therefore present a conversion algorithm capable of converting IMRT plans created by any treatment planning system into mARC plans, with the hope of expanding the availability of mARC to a larger range of clinical users and researchers. As additional advantages, our implementation offers improved functionality for planning hybrid arcs and provides an equivalent step-and-shoot plan for each mARC plan, which can be used as a back-up concept in institutions where only one linac is equipped with mARC. We present a feasibility study to outline a practical implementation of mARC plan conversion using Philips Pinnacle and Prowess Panther. We present examples for three different kinds of prostate and head-and-neck plans, for 6 MV and flattening-filter-free (FFF) 7 MV photon energies, which are dosimetrically verified. It is generally more difficult to create good quality IMRT plans in Pinnacle using a large number of beams and few segments. We present different ways of optimization as examples. By careful choosing the beam and segment arrangement and inversion objectives, we achieve plan qualities similar to our usual IMRT plans. The conversion of the plans to mARC format yields functional plans, which can be irradiated without incidences. Absolute dosimetric verification of both the step-and-shoot and mARC plans by point dose measurements showed deviations below 5% local dose, mARC plans deviated from step-and-shoot plans by no more than 1%. The agreement between GafChromic film measurements of planar dose before and after mARC conversion is excellent. The comparison of the 3D dose distribution measured by PTW Octavius 729 2D-Array with the step-and-shoot plans and with the TPS is well above the pass criteria of 90% of the points falling within 5% local dose and 3 mm distance

Metal vapor vacuum arc ion sources

International Nuclear Information System (INIS)

Brown, I.G.; Dickinson, M.R.; Galvin, J.E.; Godechot, X.; MacGill, R.A.

1990-06-01

We have developed a family of metal vapor vacuum are (MEVVA) high current metal ion sources. The sources were initially developed for the production of high current beams of metal ions for heavy ion synchrotron injection for basic nuclear physics research; more recently they have also been used for metal ion implantation. A number of different embodiments of the source have been developed for these specific applications. Presently the sources operate in a pulsed mode, with pulse width of order 1 ms and repetition rate up to 100 pps. Beam extraction voltage is up to 100 kV, and since the ions produced in the vacuum arc plasma are in general multiply ionized the ion energy is up to several hundred keV. Beam current is up to several Amperes peak and around 10 mA time averaged delivered onto target. Nearly all of the solid metals of the Periodic Table have been use to produce beam. A number of novel features have been incorporated into the sources, including multiple cathodes and the ability to switch between up to 18 separate cathode materials simply and quickly, and a broad beam source version as well as miniature versions. here we review the source designs and their performance. 45 refs., 7 figs

Investigation of the ion beam of the Titan source by the time-of-flight mass spectrometer

International Nuclear Information System (INIS)

Bugaev, A.S.; Gushenets, V.V.; Nikolaev, A.G.; Yushkov, G.Yu.

2000-01-01

The Titan ion source generates wide-aperture beams of both gaseous and metal ions of various materials. The above possibility is realized on the account of combining two types of arc discharge with cold cathodes in the source discharge system. The vacuum arc, initiated between the cathode accomplished from the ion forming material, and hollow anode, is used for obtaining the metal ions. The pinch-effect low pressure arc discharge, ignited on the same hollow anode, is used for obtaining gaseous ions. The composition of ion beams, generated by the Titan source through the specially designed time-of-flight spectrometer, is studied. The spectrometer design and principle pf operation are presented. The physical peculiarities of the source functioning, influencing the ion beam composition, are discussed [ru

Neutral-beam systems for magnetic-fusion reactors

International Nuclear Information System (INIS)

Fink, J.H.

1981-01-01

Neutral beams for magnetic fusion reactors are at an early stage of development, and require considerable effort to make them into the large, reliable, and efficient systems needed for future power plants. To optimize their performance to establish specific goals for component development, systematic analysis of the beamlines is essential. Three ion source characteristics are discussed: arc-cathode life, gas efficiency, and beam divergence, and their significance in a high-energy neutral-beam system is evaluated

Collimation system for electron arc therapy

International Nuclear Information System (INIS)

Brunelli, R.J.; Carter, J.C.

1984-01-01

An electron collimation system for electron arc therapy treatments consists of a slit collimation system which is movable with the electron beam applicator and is designed to allow for dose compensation in the sagittal direction and a hoop-and-clamp assembly for final field shaping. By correctly designing the shape of the slit in the former and properly adjusting the components of the latter, it is possible to accomplish quite uniform shielding without causing any weight of the shielding material to rest on the patient. The slit collimation system has a specially shaped aperture for confining the radiation beam. The hoop-and-clamp assembly has hoops and clamps which locate shielding over the patient's body. The shielding locating clamps are adjustably movable radially with respect to the hoops. (author)

Emittance measurements of high charge state argon beams from a pig source

International Nuclear Information System (INIS)

Bex, L.; Clark, D.J.; Ellsworth, C.E.; Estrella, R.M.; Gough, R.A.; Holley, W.R.

1975-10-01

The emittances of beams of Ar 4+ to Ar 8+ were measured in the axial and radial planes. The extraction voltage was 10 kV and the magnetic field was varied from about 0.5 to 0.6 Tesla. The anode slit was varied in distance from the arc, which was run both dc and pulsed. The emittance was nearly independent of charge state, but increased with total beam current. A small bowing of the arc column, which made evaluation of mirror field effects difficult, was discovered

Techniques to produce and accelerate radioactive ion beams

CERN Document Server

Penescu, Liviu Constantin; Lettry, Jacques; Cata-Danil, Gheorghe

The production and acceleration of the Radioactive Ion Beams (RIB) continues the long line of nuclear investigations started in the XIXth century by Pierre and Marie Curie, Henri Becquerel and Ernest Rutherford. The contemporary applications of the RIBs span a wide range of physics fields: nuclear and atomic physics, solid-state physics, life sciences and material science. ISOLDE is a world-leading Isotope mass-Separation On-Line (ISOL) facility hosted at CERN in Geneva for more than 40 years, offering the largest variety of radioactive ion beams with, until now, more than 1000 isotopes of more than 72 elements (with Z ranging from 2 to 88), with half-lives down to milliseconds and intensities up to 1011 ions/s. The post acceleration of the full variety of beams allows reaching final energies between 0.8 and 3.0 MeV/u. This thesis describes the development of a new series of FEBIAD (“Forced Electron Beam Induced Arc Discharge”) ion sources at CERN-ISOLDE. The VADIS (“Versatile Arc Discharge Ion Source�...

A Study of volumetric modulated arc therapy for stereotactic body radiation therapy in case of multi-target liver cancer using flattening filter free beam

International Nuclear Information System (INIS)

Yeom, Mi Sook; Yoon, In Ha; Hong, Dong Gi; Back, Geum Mun

2015-01-01

Stereotactic body radiation therapy (SBRT) has proved its efficacy in several patient populations with primary and metastatic limited tumors. Because SBRT prescription is high dose level than Conventional radiation therapy. SBRT plan is necessary for effective Organ at risk (OAR) protection and sufficient Planning target volume (PTV) dose coverage. In particular, multi-target cases may result excessive doses to OAR and hot spot due to dose overlap. This study evaluate usefulness of Volumetric modulated arc therapy (VMAT) in dosimetric and technical considerations using Flattening filter free (FFF) beam. The treatment plans for five patients, being treated on TrueBeam STx(Varian™, USA) with VMAT using 10MV FFF beam and Standard conformal radiotherapy (CRT) using 15MV Flattening filter (FF) beam. PTV, liver, duodenum, bowel, spinal cord, esophagus, stomach dose were evaluated using the dose volume histogram(DVH). Conformity index(CI), homogeneity index(HI), Paddick's index(PCI) for the PTV was assessed. Total Monitor unit (MU) and beam on time was assessed. Average value of CI, HI and PCI for PTV was 1.381±0.028, 1.096±0.016, 0.944±0.473 in VMAT and 1.381± 0.042, 1.136±0.042, 1.534±0.465 in CRT respectively. OAR dose in CRT plans evaluated 1.8 times higher than VMAT. Total MU in VMAT evaluated 1.3 times increase than CRT. Average beam on time was 6.8 minute in VMAT and 21.3 minute in CRT respectively. OAR dose in CRT plans evaluated 1.8 times higher than VMAT. Total MU in VMAT evaluated 1.3 times increase than CRT. Average beam on time was 6.8 minute in VMAT and 21.3 minute in CRT. VMAT for SBRT in multi-target liver cancer using FFF beam is effective treatment techniqe in dosimetric and technical considerations. VMAT decrease intra-fraction error due to treatment time shortening using high dose rate of FFF beam

A Study of volumetric modulated arc therapy for stereotactic body radiation therapy in case of multi-target liver cancer using flattening filter free beam

Energy Technology Data Exchange (ETDEWEB)

Yeom, Mi Sook; Yoon, In Ha; Hong, Dong Gi; Back, Geum Mun [Dept. of Radiation Oncology, ASAN Medical Center, Seoul (Korea, Republic of)

2015-06-15

Stereotactic body radiation therapy (SBRT) has proved its efficacy in several patient populations with primary and metastatic limited tumors. Because SBRT prescription is high dose level than Conventional radiation therapy. SBRT plan is necessary for effective Organ at risk (OAR) protection and sufficient Planning target volume (PTV) dose coverage. In particular, multi-target cases may result excessive doses to OAR and hot spot due to dose overlap. This study evaluate usefulness of Volumetric modulated arc therapy (VMAT) in dosimetric and technical considerations using Flattening filter free (FFF) beam. The treatment plans for five patients, being treated on TrueBeam STx(Varian™, USA) with VMAT using 10MV FFF beam and Standard conformal radiotherapy (CRT) using 15MV Flattening filter (FF) beam. PTV, liver, duodenum, bowel, spinal cord, esophagus, stomach dose were evaluated using the dose volume histogram(DVH). Conformity index(CI), homogeneity index(HI), Paddick's index(PCI) for the PTV was assessed. Total Monitor unit (MU) and beam on time was assessed. Average value of CI, HI and PCI for PTV was 1.381±0.028, 1.096±0.016, 0.944±0.473 in VMAT and 1.381± 0.042, 1.136±0.042, 1.534±0.465 in CRT respectively. OAR dose in CRT plans evaluated 1.8 times higher than VMAT. Total MU in VMAT evaluated 1.3 times increase than CRT. Average beam on time was 6.8 minute in VMAT and 21.3 minute in CRT respectively. OAR dose in CRT plans evaluated 1.8 times higher than VMAT. Total MU in VMAT evaluated 1.3 times increase than CRT. Average beam on time was 6.8 minute in VMAT and 21.3 minute in CRT. VMAT for SBRT in multi-target liver cancer using FFF beam is effective treatment techniqe in dosimetric and technical considerations. VMAT decrease intra-fraction error due to treatment time shortening using high dose rate of FFF beam.

Performance of a modified DuoPIGatron ion source for PLT neutral beam injectors

International Nuclear Information System (INIS)

Tsai, C.C.; Stirling, W.L.; Haselton, H.H.

1978-09-01

The performance of a modified duoPIGatron ion source for PLT neutral beam injectors is described. The 22-cm source has been operated to deliver beams of 70 A, up to 45 keV, and 0.5 sec. Following a brief review of source operation, the dominant reactions leading to an enhanced atomic ion fraction in the source plasma are emphasized. In addition to the high atomic ion species yield (about 85%), other important characteristics of the source such as high arc efficiency (about 1.1 A ion beam current per kW of arc power), long filament lifetime, high reliability, and scalability are also described

Wakefield effects in the SLC beam delivery system

International Nuclear Information System (INIS)

Napoly, O.

1996-06-01

Wakefield effects occurring in the SLC after the LI28 emittance measurement station could be responsible for part of all of the observed discrepancy between the expected vertical spot sizes at the IP and the measured ones. The strongest wakefields are generated by the parts of the beam chamber which are the closest to the beam, like collimators. In this note we review the effect of the following wakefield sources: geometric wakefields from final focus fixed and movable collimators, geometric and resistive wakefields from linac collimators jaws, resistive wakefields from the beam pipe at the sextupole and final transformer locations. We mostly concentrate on the transverse dipole and quadrupole wakefield effects, although the longitudinal wakefields are briefly studied at the end. We limit ourselves to the vertical beam dynamics and to the lowest (mainly linear) order of the wakefield expansion with respect to the beam offset, which excludes the near wall effect on the beam. (author)

Investigating the Influence of Micro-Arc Oxide Coating on Rigidity and Strength of Long Force Elements of Spacecraft

Directory of Open Access Journals (Sweden)

V. K. Shatalov

2014-01-01

Full Text Available Outboard elements (arms, towers are widely used in spacecraft structure for setting-out of a payload; their high stiffness-weight ratio provides an opportunity to decrease the mass. The deployment unit is considered as an example of outboard structure. Its strength beams work under special conditions in operation. At the transportation stage beams are under considerable vibration loads. Therefore for increasing the natural resonance frequency it is rational to increase their rigidity. Using the micro-arc oxide coating suggests itself because the modulus of elasticity of the micro-arc oxide coating is more than that of the aluminium alloy. The beams suffer considerable bending load at the step of deploying; therefore the aluminium alloy with the micro-arc oxide coating must have suitable loading capacity, in addition to increased rigidity.Influence of micro-arc oxide coating on the rigidity and strength of tubes f rom aluminium alloy is investigated. It is determined that forming the micro-arc oxide coating on thin-walled tubes with a ratio of the coating area to the cross-section area of more than 25% is the most rational. In this case the rigidity of composite material considerably exceeds the rigidity of the aluminium alloy of the same cross-section while the redistribution of stresses in the surface coating of heterogeneous elasticity cross-section doesn’t cause the sudden increase of stresses. Also forming an attainable thickness of the micro-arc oxide coating on the surface of tube from aluminium alloy will be rational solution because the increase of attainable thickness of the microarc oxide coating provides an opportunity to form it on thick-walled tubes saving an acceptable, in the context of the strength, ratio of the coating area to the overall cross-section area.Micro-arc oxidation is an advanced method to form the wear resistant, resistant to corrosion, heat-shielding and electrically insulating coatings, but depending on the

Under-reported dosimetry errors due to interplay effects during VMAT dose delivery in extreme hypofractionated stereotactic radiotherapy.

Science.gov (United States)

Gauer, Tobias; Sothmann, Thilo; Blanck, Oliver; Petersen, Cordula; Werner, René

2018-06-01

Radiotherapy of extracranial metastases changed from normofractioned 3D CRT to extreme hypofractionated stereotactic treatment using VMAT beam techniques. Random interaction between tumour motion and dynamically changing beam parameters might result in underdosage of the CTV even for an appropriately dimensioned ITV (interplay effect). This study presents a clinical scenario of extreme hypofractionated stereotactic treatment and analyses the impact of interplay effects on CTV dose coverage. For a thoracic/abdominal phantom with an integrated high-resolution detector array placed on a 4D motion platform, dual-arc treatment plans with homogenous target coverage were created using a common VMAT technique and delivered in a single fraction. CTV underdosage through interplay effects was investigated by comparing dose measurements with and without tumour motion during plan delivery. Our study agrees with previous works that pointed out insignificant interplay effects on target coverage for very regular tumour motion patterns like simple sinusoidal motion. However, we identified and illustrated scenarios that are likely to result in a clinically relevant CTV underdosage. For tumour motion with abnormal variability, target coverage quantified by the CTV area receiving more than 98% of the prescribed dose decreased to 78% compared to 100% at static dose measurement. This study is further proof of considerable influence of interplay effects on VMAT dose delivery in stereotactic radiotherapy. For selected conditions of an exemplary scenario, interplay effects and related motion-induced target underdosage primarily occurred in tumour motion pattern with increased motion variability and VMAT plan delivery using complex MLC dose modulation.

Sci-Thur PM - Colourful Interactions: Highlights 08: ARC TBI using Single-Step Optimized VMAT Fields

International Nuclear Information System (INIS)

Hudson, Alana; Gordon, Deborah; Moore, Roseanne; Balogh, Alex; Pierce, Greg

2016-01-01

Purpose: This work outlines a new TBI delivery technique to replace a lateral POP full bolus technique. The new technique is done with VMAT arc delivery, without bolus, treating the patient prone and supine. The benefits of the arc technique include: increased patient experience and safety, better dose conformity, better organ at risk sparing, decreased therapist time and reduction of therapist injuries. Methods: In this work we build on a technique developed by Jahnke et al. We use standard arc fields with gantry speeds corrected for varying distance to the patient followed by a single step VMAT optimization on a patient CT to increase dose inhomogeneity and to reduce dose to the lungs (vs. blocks). To compare the arc TBI technique to our full bolus technique, we produced plans on patient CTs for both techniques and evaluated several dosimetric parameters using an ANOVA test. Results and Conclusions: The arc technique is able reduce both the hot areas to the body (D2% reduced from 122.2% to 111.8% p<0.01) and the lungs (mean lung dose reduced from 107.5% to 99.1%, p<0.01), both statistically significant, while maintaining coverage (D98% = 97.8% vs. 94.6%, p=0.313, not statistically significant). We developed a more patient and therapist-friendly TBI treatment technique that utilizes single-step optimized VMAT plans. It was found that this technique was dosimetrically equivalent to our previous lateral technique in terms of coverage and statistically superior in terms of reduced lung dose.

Sci-Thur PM - Colourful Interactions: Highlights 08: ARC TBI using Single-Step Optimized VMAT Fields

Energy Technology Data Exchange (ETDEWEB)

Hudson, Alana; Gordon, Deborah; Moore, Roseanne; Balogh, Alex; Pierce, Greg [Tom Baker Cancer Centre (Canada)

2016-08-15

Purpose: This work outlines a new TBI delivery technique to replace a lateral POP full bolus technique. The new technique is done with VMAT arc delivery, without bolus, treating the patient prone and supine. The benefits of the arc technique include: increased patient experience and safety, better dose conformity, better organ at risk sparing, decreased therapist time and reduction of therapist injuries. Methods: In this work we build on a technique developed by Jahnke et al. We use standard arc fields with gantry speeds corrected for varying distance to the patient followed by a single step VMAT optimization on a patient CT to increase dose inhomogeneity and to reduce dose to the lungs (vs. blocks). To compare the arc TBI technique to our full bolus technique, we produced plans on patient CTs for both techniques and evaluated several dosimetric parameters using an ANOVA test. Results and Conclusions: The arc technique is able reduce both the hot areas to the body (D2% reduced from 122.2% to 111.8% p<0.01) and the lungs (mean lung dose reduced from 107.5% to 99.1%, p<0.01), both statistically significant, while maintaining coverage (D98% = 97.8% vs. 94.6%, p=0.313, not statistically significant). We developed a more patient and therapist-friendly TBI treatment technique that utilizes single-step optimized VMAT plans. It was found that this technique was dosimetrically equivalent to our previous lateral technique in terms of coverage and statistically superior in terms of reduced lung dose.

Emittance measurements of high charge state argon beams from a PIG source

International Nuclear Information System (INIS)

Bex, L.; Clark, D.J.; Ellsworth, C.E.; Estrella, R.M.; Gough, R.A.; Holley, W.R.

1976-01-01

The emittances of beams of Ar 4+ to Ar 8+ were measured in the axial and radial planes. The extraction voltage was 10 kV and the magnetic field was varied from about 0.5 to 0.6 Tesla. The anode slit was varied in its distance from the arc which was run both dc and pulsed. The emittance was found to be nearly independent of charge state but to increase with total beam current. A small bowing of the arc column was discovered, which made evaluation of mirror field effects difficult

Correlation between corrosion resistance properties and thermal cycles experienced by gas tungsten arc welding and laser beam welding Alloy 690 butt weldments

International Nuclear Information System (INIS)

Lee, H T; Wu, J L

2009-01-01

This study investigates the correlation between the thermal cycles experienced by Alloy 690 weldments fabricated using gas tungsten arc welding (GTAW) and laser beam welding (LBW) processes, and their corresponding corrosion resistance properties. The corrosion resistance of the weldments is evaluated using a U-bend stress corrosion test in which the specimens are immersed in a boiling, acid solution for 240 h. The experimental results reveal that the LBW inputs significantly less heat to the weldment than the GTAW, and therefore yields a far faster cooling rate. Moreover, the corrosion tests show that in the GTAW specimen, intergranular corrosion (IGC) occurs in both the fusion zone (FZ) and the heat affected zone (HAZ). By contrast, the LBW specimen shows no obvious signs of IGC.

Latest MIG, TIG arc-YAG laser hybrid welding systems for various welding products

Science.gov (United States)

Ishide, Takashi; Tsubota, Shuho; Watanabe, Masao

2003-03-01

Laser welding is capable of high-efficiency low-strain welding, and so its applications are started to various products. We have also put the high-power YAG laser of up to 10 kW to practical welding use for various products. On the other hand the weakest point of this laser welding is considered to be strict in the welding gap aiming allowance. In order to solve this problem, we have developed hybrid welding of TIG, MIG arc and YAG laser, taking the most advantages of both the laser and arc welding. Since the electrode is coaxial to the optical axis of the YAG laser in this process, it can be applied to welding of various objects. In the coaxial MIG, TIG-YAG welding, in order to make irradiation positions of the YAG laser beams having been guided in a wire or an electrode focused to the same position, the beam transmitted in fibers is separated to form a space between the separated beams, in which the laser is guided. With this method the beam-irradiating area can be brought near or to the arc-generating point. This enables welding of all directions even for the member of a three-dimensional shape. This time we carried out welding for various materials and have made their welding of up to 1 mm or more in welding groove gap possible. We have realized high-speed 1-pass butt welding of 4m/min in welding speed with the laser power of 3 kW for an aluminum alloy plate of approximately 4 mm thick. For a mild steel plate also we have realized butt welding of 1m/min with 5 kW for 6 mm thick. Further, in welding of stainless steel we have shown its welding possibility, by stabilizing the arc with the YAG laser in the welding atmosphere of pure argon, and shown that this welding is effective in high-efficiency welding of various materials. Here we will report the fundamental welding performances and applications to various objects for the coaxial MIG, TIG-YAG welding we have developed.

On arc efficiency in gas tungsten arc welding

Directory of Open Access Journals (Sweden)

Nils Stenbacka

2013-12-01

Full Text Available The aim of this study was to review the literature on published arc efficiency values for GTAW and, if possible, propose a narrower band. Articles between the years 1955 - 2011 have been found. Published arc efficiency values for GTAW DCEN show to lie on a wide range, between 0.36 to 0.90. Only a few studies covered DCEP - direct current electrode positive and AC current. Specific information about the reproducibility in calorimetric studies as well as in modeling and simulation studies (considering that both random and systematic errors are small was scarce. An estimate of the average arc efficiency value for GTAW DCEN indicates that it should be about 0.77. It indicates anyway that the GTAW process with DCEN is an efficient welding method. The arc efficiency is reduced when the arc length is increased. On the other hand, there are conflicting results in the literature as to the influence of arc current and travel speed.

What are the differences for IMRT plans configured with beam data collected with either the jaws or the MLCs

International Nuclear Information System (INIS)

Jolly, D.J.; Alahakone, D.; Meyer, J.

2010-01-01

Full text: The anisotropic analytic algorithm (AAA) is currently the most widely used dose calculation algorithm for photons within the Eclipse treatment planning system. Configuration of this algorithm requires field profiles, percentage depth doses and output factors for a wide range of field sizes, usually measured with the jaws defining the field. However, delivery of complex fields such as required for rotational IMRT beam shaping is done with the MLC. The purpose of this work is to determine if significant differences result between two separately configured AAA algorithms, one using beam data collected with the jaw defining the field and the other with the MLC. Methods Two separate sets of beam data were collected, one with the jaw and one with the MLC defining the field. Each set of data was then used to configure two distinct AAA algorithms. A variety of comparisons were made using various IMRT techniques including sliding window, step and shoot, RapidArc and segmented fields, calculated with both algorithms. Plan differences are presented along with verification measurements made with TLDs and the diode based ArcCheck device. Results The largest differences observed were at the surface and in highly modulated areas. The magnitude of the differences was on the order of 0.5%; with the MLC defined AAA predicting more dose than the jaw defined AAA. Discussion and Conclusion Although these initial results reveal only small differences, a full analysis of all plans will be presented before conclusions can be made as to what algorithm should be implemented clinically.

Some experiences from the commissioning program of the SLC arcs

International Nuclear Information System (INIS)

Fischer, G.E.; Brown, K.L.; Bulos, F.; Fieguth, T.; Hutton, A.; Murray, J.J.; Toge, N.; Weng, W.T.; Wiedemann, H.

1987-01-01

The SLC Arc System is designed to transport beams of electrons and positrons from the end of the SLAC Linac to the beginning of the Final Focus System where they are made to collide head on. To minimize phase space dilution caused by quantum processes in the synchrotron radiation energy loss mechanism, the bending radii are large (279 m) and very high gradient (n = 32824) AG cells are arranged in trains of low dispersion, terrain following achromats. First experiences in operating a system of over 900 magnets, each with beam position monitors and corrector magnet movers, spanning 9000 feet, are described

Eddy intrusion of hot plasma into the polar cap and formation of polar-cap arcs

International Nuclear Information System (INIS)

Chiu, Y.T.; Gorney, D.J.

1983-01-01

We present plasma and electric field data obtained by the S3-3 satellite over the polar caps. We demonstrate that: (1) plasma signatures in the polar cap arc formation region near 5000 km altitude show clear intrusions of plasma sheet (approx.keV) and magneto sheath (approx.100 eV) plasma into a background of low-energy polar cap plasma; (2) the combined plasma and electric field signatures (electron inverted-V, ion beam and delxE<0) are exactly the same as in the evening discrete arc. We interpret this equivalence of polar cap and evening discrete arc signatures as indication that their formation processes are identical. The spatial structures of polar cap electric fields and the associated plasma signatures are consistent with the hypothesis that plasma intrusion into the polar cap takes the form of multiple cellular eddies. This hypothesis provides a unifying view of arc formation and arc configurations

Negative-ion-beam generation with the ORNL SITEX source

International Nuclear Information System (INIS)

Dagenhart, W.K.; Stirling, W.L.; Kim, J.

1982-05-01

Parametric studies were made on a hot cathode reflex discharge H - Surface Ionization source with Transverse Extraction (SITEX) in both the pure hydrogen and the mixed hydrogen-cesium mode. Extraction current density, beam current, gas efficiency, extracted electron-to-H - current ratio, heavy negative ion impurities, optics, and long pulse operation were investigated as a function of time, arc voltage, arc current, converter voltage, H 2 gas flow, cesium feed rate, and plasma generator geometries. Initial results of the research were an extracted H - beam current density of 56 mA/cm 2 at 23 mA for 5 s pulses and, gas efficiency of 3%, theta/sub perpendicular/ (1/e) approx. 2 +- 1 0 , theta/sub parallel/ (1/e) approx. 1 +- 1 0 , at a beam energy of 25 keV. Negative heavy ion beam impurities were reduced to - ions are produced prinicpally by positive ion surface conversion using elemental cesium fractional monolayer coverage on a molybdenum converter substrate, which is biased negatively with respect to the anode

Optimization approaches to volumetric modulated arc therapy planning

Energy Technology Data Exchange (ETDEWEB)

Unkelbach, Jan, E-mail: junkelbach@mgh.harvard.edu; Bortfeld, Thomas; Craft, David [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114 (United States); Alber, Markus [Department of Medical Physics and Department of Radiation Oncology, Aarhus University Hospital, Aarhus C DK-8000 (Denmark); Bangert, Mark [Department of Medical Physics in Radiation Oncology, German Cancer Research Center, Heidelberg D-69120 (Germany); Bokrantz, Rasmus [RaySearch Laboratories, Stockholm SE-111 34 (Sweden); Chen, Danny [Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Li, Ruijiang; Xing, Lei [Department of Radiation Oncology, Stanford University, Stanford, California 94305 (United States); Men, Chunhua [Department of Research, Elekta, Maryland Heights, Missouri 63043 (United States); Nill, Simeon [Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London SM2 5NG (United Kingdom); Papp, Dávid [Department of Mathematics, North Carolina State University, Raleigh, North Carolina 27695 (United States); Romeijn, Edwin [H. Milton Stewart School of Industrial and Systems Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Salari, Ehsan [Department of Industrial and Manufacturing Engineering, Wichita State University, Wichita, Kansas 67260 (United States)

2015-03-15

Volumetric modulated arc therapy (VMAT) has found widespread clinical application in recent years. A large number of treatment planning studies have evaluated the potential for VMAT for different disease sites based on the currently available commercial implementations of VMAT planning. In contrast, literature on the underlying mathematical optimization methods used in treatment planning is scarce. VMAT planning represents a challenging large scale optimization problem. In contrast to fluence map optimization in intensity-modulated radiotherapy planning for static beams, VMAT planning represents a nonconvex optimization problem. In this paper, the authors review the state-of-the-art in VMAT planning from an algorithmic perspective. Different approaches to VMAT optimization, including arc sequencing methods, extensions of direct aperture optimization, and direct optimization of leaf trajectories are reviewed. Their advantages and limitations are outlined and recommendations for improvements are discussed.

Feasibility of Single-Isocenter Volumetric Modulated Arc Radiosurgery for Treatment of Multiple Brain Metastases

International Nuclear Information System (INIS)

Clark, Grant M.; Popple, Richard A.; Young, P. Edward; Fiveash, John B.

2010-01-01

Purpose: To evaluate the relative plan quality of single-isocenter vs. multi-isocenter volumetric modulated arc therapy (VMAT) for radiosurgical treatment of multiple central nervous system metastases. Methods and Materials: VMAT plans were created using RapidArc technology for treatment of simulated patients with three brain metastases. The plans consisted of single-arc/single-isocenter, triple-arc (noncoplanar)/single-isocenter, and triple-arc (coplanar)/triple-isocenter configurations. All VMAT plans were normalized to deliver 100% of the 20-Gy prescription dose to all lesions. The plans were evaluated by calculation of Paddick and Radiation Therapy Oncology Group conformity index scores, Paddick gradient index scores, and 12-Gy isodose volumes. Results: All plans were judged clinically acceptable, but differences were observed in the dosimetric parameters, with the use of multiple noncoplanar arcs showing small improvements in the conformity indexes compared with the single-arc/single-isocenter and triple-arc (coplanar)/triple-isocenter plans. Multiple arc plans (triple-arc [noncoplanar]/single-isocenter and triple-arc [coplanar]/triple-isocenter) showed smaller 12-Gy isodose volumes in scenarios involving three metastases spaced closely together, with only small differences noted among all plans involving lesions spaced further apart. Conclusion: Our initial results suggest that single-isocenter VMAT plans can be used to deliver conformity equivalent to that of multiple isocenter VMAT techniques. For targets that are closely spaced, multiple noncoplanar single-isocenter arcs might be required. VMAT radiosurgery for multiple targets using a single isocenter can be efficiently delivered, requiring less than one-half the beam time required for multiple isocenter set ups. VMAT radiosurgery will likely replace multi-isocenter techniques for linear accelerator-based treatment of multiple targets.

SU-G-BRC-14: Multi-Lesion, Multi-Rx, Brain Radiosurgery with Novel Single Isocenter Technique

Energy Technology Data Exchange (ETDEWEB)

Honig, N; Alani, S; Schlocker, A; Shtraus, N; Kanner, A [B Corn Tel Aviv Medical Center, Tel Aviv (Israel)

2016-06-15

Purpose: There is a strong trend to treat multiple brain metastases with radiosurgery rather than whole brain irradiation. This feasibility study investigates a novel planning technique for radio-surgical treatment of multiple brain lesions with differing dose prescriptions, a single isocenter, and dynamic conformal arcs. The novel technique will be compared to the well-established single-isocenter volumetric modulated arc therapy (VMAT) technique commonly used for treating brain lesions. Methods: Six patients with metastatic brain lesions were selected for a prospective treatment planning study to evaluate Interdigitating MLC Dynamic Conformal Arc (IMDCA) technique. Arcs were planned for simultaneous irradiation to maximize beam delivery efficiency. To accommodate varying PTV dose prescriptions, selected arcs were re-irradiated in reverse. Beam weights were adjusted until all prescription constraints were met. The number of lesions ranged between 2 to 4 (mode = 3). For comparison, SRS VMAT plans were generated utilizing an established single-isocenter, 3 arc planning template. All plans were compared by means of Paddick conformity index (PCI), RTOG Conformity Index (RCI), gradient index (GI), and the normal brain volume receiving 10% (V10) of the highest prescription dose. The monitor units and delivery time were tabulated for each plan. Results: IMDCA achieved conformal plans (PCI = 0.72±0.03, RCI = 1.33±0.03) with steep dose fall-off (GI = 3.79±0.03) on average for all of the plans evaluated. The VMAT plans had slightly better conformity (PCI = 0.85 ± 0.03, RCI = 1.13 ± 0.03) than IMDCA, but overall worse GI (4.29 ± 0.06). IMDCA plans had lower V10% values, required 50% fewer MUs, and had 34% shorter beam delivery time on average compared to VMAT plans. Conclusion: IMDCA plans with varying dose prescriptions for multiple lesions, had comparable dosimetric coverage as VMAT plans, but were obtained with significantly lower integral dose, fewer monitor units

SU-G-BRC-14: Multi-Lesion, Multi-Rx, Brain Radiosurgery with Novel Single Isocenter Technique

International Nuclear Information System (INIS)

Honig, N; Alani, S; Schlocker, A; Shtraus, N; Kanner, A

2016-01-01

Purpose: There is a strong trend to treat multiple brain metastases with radiosurgery rather than whole brain irradiation. This feasibility study investigates a novel planning technique for radio-surgical treatment of multiple brain lesions with differing dose prescriptions, a single isocenter, and dynamic conformal arcs. The novel technique will be compared to the well-established single-isocenter volumetric modulated arc therapy (VMAT) technique commonly used for treating brain lesions. Methods: Six patients with metastatic brain lesions were selected for a prospective treatment planning study to evaluate Interdigitating MLC Dynamic Conformal Arc (IMDCA) technique. Arcs were planned for simultaneous irradiation to maximize beam delivery efficiency. To accommodate varying PTV dose prescriptions, selected arcs were re-irradiated in reverse. Beam weights were adjusted until all prescription constraints were met. The number of lesions ranged between 2 to 4 (mode = 3). For comparison, SRS VMAT plans were generated utilizing an established single-isocenter, 3 arc planning template. All plans were compared by means of Paddick conformity index (PCI), RTOG Conformity Index (RCI), gradient index (GI), and the normal brain volume receiving 10% (V10) of the highest prescription dose. The monitor units and delivery time were tabulated for each plan. Results: IMDCA achieved conformal plans (PCI = 0.72±0.03, RCI = 1.33±0.03) with steep dose fall-off (GI = 3.79±0.03) on average for all of the plans evaluated. The VMAT plans had slightly better conformity (PCI = 0.85 ± 0.03, RCI = 1.13 ± 0.03) than IMDCA, but overall worse GI (4.29 ± 0.06). IMDCA plans had lower V10% values, required 50% fewer MUs, and had 34% shorter beam delivery time on average compared to VMAT plans. Conclusion: IMDCA plans with varying dose prescriptions for multiple lesions, had comparable dosimetric coverage as VMAT plans, but were obtained with significantly lower integral dose, fewer monitor units

Preparation and investigation of diamond-like carbon stripper foils by filtered cathodic vacuum arc

International Nuclear Information System (INIS)

Fan, Qiwen; Du, Yinghui; Zhang, Rong; Xu, Guoji

2013-01-01

Thin diamond-like carbon (DLC) stripper foils ∼5μg/cm 2 in thickness were produced and evaluated as heavy-ion strippers for the Beijing HI-13 Tandem Accelerator. The DLC layers ∼4μg/cm 2 in thickness were produced by the filtered cathodic vacuum arc technology onto glass slides coated with betaine–saccharose as releasing agent, which were previously covered with evaporated carbon layers ∼1μg/cm 2 in thickness by the controlled ac arc-discharge method. Irradiation lifetimes of the DLC stripper foils were tested using the heavy-ion beams at the terminal of the Beijing HI-13 Tandem Accelerator, and compared with those of the standard carbon stripper foils made by the combined dc and ac arc-discharge method. The measurements indicate that the DLC stripper foils outlast the standard combined dc and ac arc-discharge carbon stripper foils by a factor of at least 13 and 4 for the 197 Au − (∼9MeV, ∼1μA) and 63 Cu − (∼9MeV, ∼1μA) ion beams, respectively. The structure and properties of the DLC foils deposited onto silicon substrates by the filtered cathodic vacuum arc technology were also evaluated and analyzed by scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The scanning electron microscopy images show that the DLC foils contain hardly droplets through the double 90° filters. The X-ray photoelectron spectrum indicates that sp 3 bonds of the DLC foils exceed 70%. The integral intensity ratio of the D peak to the G peak (I D /I G ) measured by the Raman spectroscopy is 0.78

Electron arc therapy: Influence of heterogeneities on dose to blood-forming organs

International Nuclear Information System (INIS)

Leavitt, D.D.; Gibbs, F.A.; Moeller, J.H.

1986-01-01

Electron arc therapy has been used successfully to treat extended chest wall surfaces after mastectomy. Treatment is frequently given simultaneously with chemotherapy. Although the primary electron arc treatment volume consists only of the chest wall and mediastinum, dose is accumulated at the isocenter of rotation due to the photon contamination of the arcing electron beam. Additionally, higher energy electron fields which are occasionally used over segments of the arc may contribute to the dose at isocenter if the electron range has been extended due to passage through a low-density heterogeneity such as lung. In some patient setups, the isocenter may intersect blood-forming organs, such as the vertebral bodies. Thermoluminescent dosimetry has been used to measure the dose at isocenter for the following setups: polystyrene phantom, polystyrene phantom covered by 1-cm-thick lead cast, polystyrene phantom with cork insert to simulate lung, and phantom plus cork insert plus lead cast. For the 9-MeV treatment mode, dose at isocenter per 90 0 of arc (as a percentage of maximum tumor dose) is as follows: phantom, 6.5%; phantom plus lead, 5%; phantom plus cork, 8%; and phantom plus cork plus lead, 6%. These values must be scaled by the size of the arc to estimate dose at isocenter in actual treatments. Computer calculation showed good agreement with these measured values, indicating that the computerized treatment plans can be used as a predictor of electron arc dose to blood-forming organs

Optics of ion beams for the neutral beam injection system on HL-2A Tokamak

Energy Technology Data Exchange (ETDEWEB)

Zou, G. Q.; Lei, G. J.; Cao, J. Y.; Duan, X. R. [Southwestern Institute of Physics, Chengdu, 610041 (China)

2012-07-15

The ion beam optics for the neutral beam injection system on HL-2A Tokomak is studied by two- dimensional numerical simulation program firstly, where the emitting surface is taken at 100 Debye lengths from the plasma electrode. The mathematical formulation, computation techniques are described. Typical ion orbits, equipotential contours, and emittance diagram are shown. For a fixed geometry electrode, the effect of plasma density, plasma potential and plasma electron temperature on ion beam optics is examined, and the calculation reliability is confirmed by experimental results. In order to improve ion beam optics, the application of a small pre-acceleration voltage ({approx}100 V) between the plasma electrode and the arc discharge anode is reasonable, and a lower plasma electron temperature is desired. The results allow optimization of the ion beam optics in the neutral beam injection system on HL-2A Tokomak and provide guidelines for designing future neutral beam injection system on HL-2M Tokomak.

Optics of ion beams for the neutral beam injection system on HL-2A Tokamak.

Science.gov (United States)

Zou, G Q; Lei, G J; Cao, J Y; Duan, X R

2012-07-01

The ion beam optics for the neutral beam injection system on HL-2A Tokomak is studied by two- dimensional numerical simulation program firstly, where the emitting surface is taken at 100 Debye lengths from the plasma electrode. The mathematical formulation, computation techniques are described. Typical ion orbits, equipotential contours, and emittance diagram are shown. For a fixed geometry electrode, the effect of plasma density, plasma potential and plasma electron temperature on ion beam optics is examined, and the calculation reliability is confirmed by experimental results. In order to improve ion beam optics, the application of a small pre-acceleration voltage (∼100 V) between the plasma electrode and the arc discharge anode is reasonable, and a lower plasma electron temperature is desired. The results allow optimization of the ion beam optics in the neutral beam injection system on HL-2A Tokomak and provide guidelines for designing future neutral beam injection system on HL-2M Tokomak.

Vacuum ARC ion sources - activities ampersand developments at LBL

International Nuclear Information System (INIS)

Brown, I.

1996-01-01

The author describes work at LBL on the development and application of vacuum arc ion sources. Work has been done on vacuum spark sources - to produce very high charge states, studies of high charge states in magnetic field, hybrid ion source operation on metal/gas plasma, multipole operation, work on MEVVA V for implantation applications, development of broad beam sources, and removal of particles from the output of the source

Application of YAG Laser TIG Arc Hybrid Welding to Thin AZ31B Magnesium Alloy Sheet

Science.gov (United States)

Kim, Taewon; Kim, Jongcheol; Hasegawa, Yu; Suga, Yasuo

A magnesium alloy is said to be an ecological material with high ability of recycling and lightweight property. Especially, magnesium alloys are in great demand on account of outstanding material property as a structural material. Under these circumstances, research and development of welding process to join magnesium alloy plates are of great significance for wide industrial application of magnesium. In order to use it as a structure material, the welding technology is very important. TIG arc welding process is the most ordinary process to weld magnesium alloy plates. However, since the heat source by the arc welding process affects the magnesium alloy plates, HAZ of welded joint becomes wide and large distortion often occurs. On the other hand, a laser welding process that has small diameter of heat source seems to be one of the possible means to weld magnesium alloy in view of the qualitative improvement. However, the low boiling point of magnesium generates some weld defects, including porosity and solidification cracking. Furthermore, precise edge preparation is very important in butt-welding by the laser welding process, due to the small laser beam diameter. Laser/arc hybrid welding process that combines the laser beam and the arc is an effective welding process in which these two heat sources influence and assist each other. Using the hybrid welding, a synegistic effect is achievable and the disadvantages of the respective processes can be compensated. In this study, YAG laser/TIG arc hybrid welding of thin magnesium alloy (AZ31B) sheets was investigated. First of all, the effect of the irradiation point and the focal position of laser beam on the quality of a weld were discussed in hybrid welding. Then, it was confirmed that a sound weld bead with sufficient penetration is obtained using appropriate welding conditions. Furthermore, it was made clear that the heat absorption efficiency is improved with the hybrid welding process. Finally, the tensile tests

Motion as a perturbation: Measurement-guided dose estimates to moving patient voxels during modulated arc deliveries

Energy Technology Data Exchange (ETDEWEB)

Feygelman, Vladimir; Zhang, Geoffrey; Hunt, Dylan; Opp, Daniel [Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612 (United States); Stambaugh, Cassandra [Department of Physics, University of South Florida, Tampa, Florida 33612 (United States); Wolf, Theresa K. [Live Oak Technologies LLC, Kirkwood, Missouri 63122 (United States); Nelms, Benjamin E. [Canis Lupus LLC, Merrimac, Wisconsin 53561 (United States)

2013-02-15

Purpose: To present a framework for measurement-guided VMAT dose reconstruction to moving patient voxels from a known motion kernel and the static phantom data, and to validate this perturbation-based approach with the proof-of-principle experiments. Methods: As described previously, the VMAT 3D dose to a static patient can be estimated by applying a phantom measurement-guided perturbation to the treatment planning system (TPS)-calculated dose grid. The fraction dose to any voxel in the presence of motion, assuming the motion kernel is known, can be derived in a similar fashion by applying a measurement-guided motion perturbation. The dose to the diodes in a helical phantom is recorded at 50 ms intervals and is transformed into a series of time-resolved high-density volumetric dose grids. A moving voxel is propagated through this 4D dose space and the fraction dose to that voxel in the phantom is accumulated. The ratio of this motion-perturbed, reconstructed dose to the TPS dose in the phantom serves as a perturbation factor, applied to the TPS fraction dose to the similarly situated voxel in the patient. This approach was validated by the ion chamber and film measurements on four phantoms of different shape and structure: homogeneous and inhomogeneous cylinders, a homogeneous cube, and an anthropomorphic thoracic phantom. A 2D motion stage was used to simulate the motion. The stage position was synchronized with the beam start time with the respiratory gating simulator. The motion patterns were designed such that the motion speed was in the upper range of the expected tumor motion (1-1.4 cm/s) and the range exceeded the normally observed limits (up to 5.7 cm). The conformal arc plans for X or Y motion (in the IEC 61217 coordinate system) consisted of manually created narrow (3 cm) rectangular strips moving in-phase (tracking) or phase-shifted by 90 Degree-Sign (crossing) with respect to the phantom motion. The XY motion was tested with the computer-derived VMAT

Motion as a perturbation: Measurement-guided dose estimates to moving patient voxels during modulated arc deliveries

International Nuclear Information System (INIS)

Feygelman, Vladimir; Zhang, Geoffrey; Hunt, Dylan; Opp, Daniel; Stambaugh, Cassandra; Wolf, Theresa K.; Nelms, Benjamin E.

2013-01-01

Purpose: To present a framework for measurement-guided VMAT dose reconstruction to moving patient voxels from a known motion kernel and the static phantom data, and to validate this perturbation-based approach with the proof-of-principle experiments. Methods: As described previously, the VMAT 3D dose to a static patient can be estimated by applying a phantom measurement-guided perturbation to the treatment planning system (TPS)-calculated dose grid. The fraction dose to any voxel in the presence of motion, assuming the motion kernel is known, can be derived in a similar fashion by applying a measurement-guided motion perturbation. The dose to the diodes in a helical phantom is recorded at 50 ms intervals and is transformed into a series of time-resolved high-density volumetric dose grids. A moving voxel is propagated through this 4D dose space and the fraction dose to that voxel in the phantom is accumulated. The ratio of this motion-perturbed, reconstructed dose to the TPS dose in the phantom serves as a perturbation factor, applied to the TPS fraction dose to the similarly situated voxel in the patient. This approach was validated by the ion chamber and film measurements on four phantoms of different shape and structure: homogeneous and inhomogeneous cylinders, a homogeneous cube, and an anthropomorphic thoracic phantom. A 2D motion stage was used to simulate the motion. The stage position was synchronized with the beam start time with the respiratory gating simulator. The motion patterns were designed such that the motion speed was in the upper range of the expected tumor motion (1–1.4 cm/s) and the range exceeded the normally observed limits (up to 5.7 cm). The conformal arc plans for X or Y motion (in the IEC 61217 coordinate system) consisted of manually created narrow (3 cm) rectangular strips moving in-phase (tracking) or phase-shifted by 90° (crossing) with respect to the phantom motion. The XY motion was tested with the computer-derived VMAT MLC

Clustering of arc volcanoes caused by temperature perturbations in the back-arc mantle.

Science.gov (United States)

Lee, Changyeol; Wada, Ikuko

2017-06-29

Clustering of arc volcanoes in subduction zones indicates along-arc variation in the physical condition of the underlying mantle where majority of arc magmas are generated. The sub-arc mantle is brought in from the back-arc largely by slab-driven mantle wedge flow. Dynamic processes in the back-arc, such as small-scale mantle convection, are likely to cause lateral variations in the back-arc mantle temperature. Here we use a simple three-dimensional numerical model to quantify the effects of back-arc temperature perturbations on the mantle wedge flow pattern and sub-arc mantle temperature. Our model calculations show that relatively small temperature perturbations in the back-arc result in vigorous inflow of hotter mantle and subdued inflow of colder mantle beneath the arc due to the temperature dependence of the mantle viscosity. This causes a three-dimensional mantle flow pattern that amplifies the along-arc variations in the sub-arc mantle temperature, providing a simple mechanism for volcano clustering.

Cardiac Exposure in the Dynamic Conformal Arc Therapy, Intensity-Modulated Radiotherapy and Volumetric Modulated Arc Therapy of Lung Cancer.

Directory of Open Access Journals (Sweden)

Xin Ming

Full Text Available To retrospectively evaluate the cardiac exposure in three cohorts of lung cancer patients treated with dynamic conformal arc therapy (DCAT, intensity-modulated radiotherapy (IMRT, or volumetric modulated arc therapy (VMAT at our institution in the past seven years.A total of 140 lung cancer patients were included in this institutional review board approved study: 25 treated with DCAT, 70 with IMRT and 45 with VMAT. All plans were generated in a same commercial treatment planning system and have been clinically accepted and delivered. The dose distribution to the heart and the effects of tumor laterality, the irradiated heart volume and the beam-to-heart distance on the cardiac exposure were investigated.The mean dose to the heart among all 140 plans was 4.5 Gy. Specifically, the heart received on average 2.3, 5.2 and 4.6 Gy in the DCAT, IMRT and VMAT plans, respectively. The mean heart doses for the left and right lung tumors were 4.1 and 4.8 Gy, respectively. No patients died with evidence of cardiac disease. Three patients (2% with preexisting cardiac condition developed cardiac disease after treatment. Furthermore, the cardiac exposure was found to increase linearly with the irradiated heart volume while decreasing exponentially with the beam-to-heart distance.Compared to old technologies for lung cancer treatment, modern radiotherapy treatment modalities demonstrated better heart sparing. But the heart dose in lung cancer radiotherapy is still higher than that in the radiotherapy of breast cancer and Hodgkin's disease where cardiac complications have been extensively studied. With strong correlations of mean heart dose with beam-to-heart distance and irradiated heart volume, cautions should be exercised to avoid long-term cardiac toxicity in the lung cancer patients undergoing radiotherapy.

Dosimetric comparison between RapidArc and fixed gantry intensity modulated radiation therapy in treatment of liver carcinoma

International Nuclear Information System (INIS)

Ma Changsheng; Yin Yong; Liu Tonghai; Chen Jinhu; Sun Tao; Lin Xiutong

2010-01-01

Objective: To compare the dosimetric difference of RapidArc and fixed gantry IMRT for liver carcinoma. Methods: The CT data of 10 liver cancer patients were used to design 3 groups of treatment plan: IMRT plan, single arc RapidArc plan (RA1), and dual arc RapidArc plan (RA2). The planning target volume (PTV) dosimetric distribution, the organs at risk (OAR) dose, the normal tissue dose, mornitor units (MU) and treatment time were compared. Results: The maximum dose of PTV in RA1 and RA2 plans were lower than that of IMRT (Z=-2.0990, -2.666, P 40 of stomach small bowel than IMRT plan, but higher in mean dose of left kidney (Z=-1.988, -2.191, P 5 , V 10 and 15 of healthy tissue in RapidArc plan groups were higher than those in IMRT plan, while the values of V 20 , V 25 and V 30 of healthy tissue in RapidArc plan groups were than those in IMRT plan. The number of computed MU/fraction of Rapid Arc plan was 40% or 46% of IMRT plan and the treatment time was 30% and 40% of IMRT. Conclusions: RapidArc showed improvements in conformity index and healthy tissue sparing with uncompromised target coverage. RapidArc could lead to the less MU and shorter delivery time compared to IMRT. (authors)

SU-F-T-273: Using a Diode Array to Explore the Weakness of TPS DoseCalculation Algorithm for VMAT and Sliding Window Techniques

Energy Technology Data Exchange (ETDEWEB)

Park, J; Lu, B; Yan, G; Park, J; Li, F; Li, J; Liu, C [University of Florida, Gainesville, FL (United States)

2016-06-15

Purpose: To identify the weakness of dose calculation algorithm in a treatment planning system for volumetric modulated arc therapy (VMAT) and sliding window (SW) techniques using a two-dimensional diode array. Methods: The VMAT quality assurance(QA) was implemented with a diode array using multiple partial arcs that divided from a VMAT plan; each partial arc has the same segments and the original monitor units. Arc angles were less than ± 30°. Multiple arcs delivered through consecutive and repetitive gantry operating clockwise and counterclockwise. The source-toaxis distance setup with the effective depths of 10 and 20 cm were used for a diode array. To figure out dose errors caused in delivery of VMAT fields, the numerous fields having the same segments with the VMAT field irradiated using different delivery techniques of static and step-and-shoot. The dose distributions of the SW technique were evaluated by creating split fields having fine moving steps of multi-leaf collimator leaves. Calculated doses using the adaptive convolution algorithm were analyzed with measured ones with distance-to-agreement and dose difference of 3 mm and 3%.. Results: While the beam delivery through static and step-and-shoot techniques showed the passing rate of 97 ± 2%, partial arc delivery of the VMAT fields brought out passing rate of 85%. However, when leaf motion was restricted less than 4.6 mm/°, passing rate was improved up to 95 ± 2%. Similar passing rate were obtained for both 10 and 20 cm effective depth setup. The calculated doses using the SW technique showed the dose difference over 7% at the final arrival point of moving leaves. Conclusion: Error components in dynamic delivery of modulated beams were distinguished by using the suggested QA method. This partial arc method can be used for routine VMAT QA. Improved SW calculation algorithm is required to provide accurate estimated doses.

Critical Length Criterion and the Arc Chain Model for Calculating the Arcing Time of the Secondary Arc Related to AC Transmission Lines

International Nuclear Information System (INIS)

Cong Haoxi; Li Qingmin; Xing Jinyuan; Li Jinsong; Chen Qiang

2015-01-01

The prompt extinction of the secondary arc is critical to the single-phase reclosing of AC transmission lines, including half-wavelength power transmission lines. In this paper, a low-voltage physical experimental platform was established and the motion process of the secondary arc was recorded by a high-speed camera. It was found that the arcing time of the secondary arc rendered a close relationship with its arc length. Through the input and output power energy analysis of the secondary arc, a new critical length criterion for the arcing time was proposed. The arc chain model was then adopted to calculate the arcing time with both the traditional and the proposed critical length criteria, and the simulation results were compared with the experimental data. The study showed that the arcing time calculated from the new critical length criterion gave more accurate results, which can provide a reliable criterion in term of arcing time for modeling and simulation of the secondary arc related with power transmission lines. (paper)

Respiratory gated beam delivery cannot facilitate margin reduction, unless combined with respiratory correlated image guidance

International Nuclear Information System (INIS)

Korreman, Stine S.; Juhler-Nottrup, Trine; Boyer, Arthur L.

2008-01-01

Purpose/objective: In radiotherapy of targets moving with respiration, beam gating is offered as a means of reducing the target motion. The purpose of this study is to evaluate the safe magnitude of margin reduction for respiratory gated beam delivery. Materials/methods: The study is based on data for 17 lung cancer patients in separate protocols at Rigshospitalet and Stanford Cancer Center. Respiratory curves for external optical markers and implanted fiducials were collected using equipment based on the RPM system (Varian Medical Systems). A total of 861 respiratory curves represented external measurements over 30 fraction treatment courses for 10 patients, and synchronous external/internal measurements in single sessions for seven patients. Variations in respiratory amplitude (simulated coaching) and external/internal phase shifts were simulated by perturbation with realistic values. Variations were described by medians and standard deviations (SDs) of position distributions of the markers. Gating windows (35% duty cycle) were retrospectively applied to the respiratory data for each session, mimicking the use of commercially available gating systems. Medians and SDs of gated data were compared to those of ungated data, to assess potential margin reductions. Results: External respiratory data collected over entire treatment courses showed SDs from 1.6 to 8.1 mm, the major part arising from baseline variations. The gated data had SDs from 1.5 to 7.7 mm, with a mean reduction of 0.3 mm (6%). Gated distributions were more skewed than ungated, and in a few cases a marginal miss of gated respiration would be found even if no margin reduction was applied. Regularization of breathing amplitude to simulate coaching did not alter these results significantly. Simulation of varying phase shifts between internal and external respiratory signals showed that the SDs of gated distributions were the same as for the ungated or smaller, but the median values were markedly shifted

An external dosimetry audit programme to credential static and rotational IMRT delivery for clinical trials quality assurance.

Science.gov (United States)

Eaton, David J; Tyler, Justine; Backshall, Alex; Bernstein, David; Carver, Antony; Gasnier, Anne; Henderson, Julia; Lee, Jonathan; Patel, Rushil; Tsang, Yatman; Yang, Huiqi; Zotova, Rada; Wells, Emma

2017-03-01

External dosimetry audits give confidence in the safe and accurate delivery of radiotherapy. The RTTQA group have performed an on-site audit programme for trial recruiting centres, who have recently implemented static or rotational IMRT, and those with major changes to planning or delivery systems. Measurements of reference beam output were performed by the host centre, and by the auditor using independent equipment. Verification of clinical plans was performed using the ArcCheck helical diode array. A total of 54 measurement sessions were performed between May 2014 and June 2016 at 28 UK institutions, reflecting the different combinations of planning and delivery systems used at each institution. Average ratio of measured output between auditor and host was 1.002±0.006. Average point dose agreement for clinical plans was -0.3±1.8%. Average (and 95% lower confidence intervals) of gamma pass rates at 2%/2mm, 3%/2mm and 3%/3mm respectively were: 92% (80%), 96% (90%) and 98% (94%). Moderately significant differences were seen between fixed gantry angle and rotational IMRT, and between combination of planning systems and linac manufacturer, but not between anatomical treatment site or beam energy. An external audit programme has been implemented for universal and efficient credentialing of IMRT treatments in clinical trials. Good agreement was found between measured and expected doses, with few outliers, leading to a simple table of optimal and mandatory tolerances for approval of dosimetry audit results. Feedback was given to some centres leading to improved clinical practice. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Arc saw development report

International Nuclear Information System (INIS)

Deichelbohrer, P.R.; Beitel, G.A.

1981-01-01

The arc saw is one of the key components of the Contaminated Equipment Volume Reduction (CEVR) Program. This report describes the progress of the arc saw from its inception to its current developmental status. History of the arc saw and early contributors are discussed. Particular features of the arc saw and their advantages for CEVR are detailed. Development of the arc saw including theory of operation, pertinent experimental results, plans for the large arc saw and advanced control systems are covered. Associated topics such as potential applications for the arc saw and other arc saw installations in the world is also touched upon

Effects of Surface Alloying and Laser Beam Treatment on the Microstructure and Wear Behaviour of Surfaces Modified Using Submerged Metal Arc Welding

Directory of Open Access Journals (Sweden)

Regita BENDIKIENE

2016-05-01

Full Text Available In this study, the effects of surface alloying of cheap plain carbon steel using submerged metal arc technique and subsequent laser beam treatment on the microstructure and wear behaviour of surfaced layers were studied. This method is the cheapest one to obtain high alloyed coatings, because there is no need to apply complex technologies of powder making (metal powder is spread on the surface of base metal or inserted into the flux, it is enough to grind, granulate and blend additional materials. On the other hand, strengthening of superficial layers of alloys by thermal laser radiation is one of the applications of laser. Surface is strengthened by concentrated laser beam focused into teeny area (from section of mm till some mm. Teeny area of metal heat up rapidly and when heat is drain to the inner metal layers giving strengthening effect. Steel surface during this treatment exceeds critical temperatures, if there is a need to strengthen deeper portions of the base metal it is possible even to fuse superficial layer. The results presented in this paper are based on micro-structural and micro-chemical analyses of the surfaced and laser beam treated surfaces and are supported by analyses of the hardness, the wear resistance and resultant microstructures. Due to the usage of waste raw materials a significant improvement (~ 30 % in wear resistance was achieved. The maximum achieved hardness of surfaced layer was 62 HRC, it can be compared with high alloyed conventional steel grade. Wear properties of overlays with additional laser beam treatment showed that weight loss of these layers was ~10 % lower compared with overlays after welding; consequently it is possible to replace high alloyed conventional steel grades forming new surfaces or restoring worn machine elements and tools.DOI: http://dx.doi.org/10.5755/j01.ms.22.1.7621

Verification of patient position and delivery of IMRT by electronic portal imaging

International Nuclear Information System (INIS)

Fielding, Andrew L.; Evans, Philip M.; Clark, Catharine H.

2004-01-01

Background and purpose: The purpose of the work presented in this paper was to determine whether patient positioning and delivery errors could be detected using electronic portal images of intensity modulated radiotherapy (IMRT). Patients and methods: We carried out a series of controlled experiments delivering an IMRT beam to a humanoid phantom using both the dynamic and multiple static field method of delivery. The beams were imaged, the images calibrated to remove the IMRT fluence variation and then compared with calibrated images of the reference beams without any delivery or position errors. The first set of experiments involved translating the position of the phantom both laterally and in a superior/inferior direction a distance of 1, 2, 5 and 10 mm. The phantom was also rotated 1 and 2 deg. For the second set of measurements the phantom position was kept fixed and delivery errors were introduced to the beam. The delivery errors took the form of leaf position and segment intensity errors. Results: The method was able to detect shifts in the phantom position of 1 mm, leaf position errors of 2 mm, and dosimetry errors of 10% on a single segment of a 15 segment IMRT step and shoot delivery (significantly less than 1% of the total dose). Conclusions: The results of this work have shown that the method of imaging the IMRT beam and calibrating the images to remove the intensity modulations could be a useful tool in verifying both the patient position and the delivery of the beam

Pre-treatment verification of RapidArc® using Electronic Portal Imaging Device; Verificacao pre-tratamento de RapidArc® utilizando Dispositivo Eletronico de Imagem Porta

Energy Technology Data Exchange (ETDEWEB)

Lima, Marilia B.; Ferreira, Anne Caroline M.; Bittencourt, Guilherme R.; Pirani, Luis F.; Silveira, Thiago B., E-mail: mbeckerlima@gmail.com [Instituto Nacional do Cancer (INCA), Rio de Janeiro, RJ (Brazil)

2012-12-15

The RapidArc® is a novel but widespread technique to achieve intensity modulated beams. One of the major challenges concerning this technique is the pretreatment verification process. The aim of this paper was to analyze the viability of the Electronic Portal Imaging Device (EPID) used to perform the verification of RapidArc® using the Sun Nuclear SNC Patient software enable to EPID dose conversion (EPIDose license) and compare its results with punctual dose measurements against a low volume ion chamber. There were analyze five RapidArc® planning, evaluating, separately, planar and punctual doses for each arc. For punctual measurements was used a 0,15 cm³ volume ion chamber and the planar distributions, in Calibration Units (CU), were acquired using the EPID and then converted to absolute dose in centigray through EPIDose. The predicted doses were calculated using the AAA algorithm in Eclipse treatment planning system, version 8.6. The planar comparisons, performed in SNC Patient, employed the Gamma Index tool with a 4% dose difference, 4 mm distance to agreement and 20% threshold. The evaluation of punctual dose was defined by calculating deviations between predicted and measured doses. The mean approval percentage in planar distributions was 94.8% and the average deviation in punctual dose was -1.2%. The use of EPID for RapidArc® pre-treatment verification proved to be feasible and showed good sensibility, because of its high spatial resolution. However one must consider the uncertainty of the method. (author)

Auroral arc classification scheme based on the observed arc-associated electric field pattern

International Nuclear Information System (INIS)

Marklund, G.

1983-06-01

Radar and rocket electric field observations of auroral arcs have earlier been used to identify essentially four different arc types, namely anticorrelation and correlation arcs (with, respectively, decreased and increased arc-assocaited field) and asymmetric and reversal arcs. In this paper rocket double probe and supplementary observations from the literature, obtained under various geophysical conditions, are used to organize the different arc types on a physical rather than morphological basis. This classification is based on the relative influence on the arc electric field pattern from the two current continuity mechanisms, polarisation electric fields and Birkeland currents. In this context the tangential electric field plays an essential role and it is thus important that it can be obtained with both high accuracy and resolution. In situ observations by sounding rockets are shown to be better suited for this specific task than monostatic radar observations. Depending on the dominating mechanism, estimated quantitatively for a number of arc-crossings, the different arc types have been grouped into the following main categories: Polarisation arcs, Birkeland current arcs and combination arcs. Finally the high altitude potential distributions corresponding to some of the different arc types are presented. (author)

Laser beam alignment and profilometry using diagnostic fluorescent safety mirrors

Science.gov (United States)

Lizotte, Todd E.

2011-03-01

There are a wide range of laser beam delivery systems in use for various purposes; including industrial and medical applications. Virtually all such beam delivery systems for practical purposes employ optical systems comprised of mirrors and lenses to shape, focus and guide the laser beam down to the material being processed. The goal of the laser beam delivery is to set the optimum parameters and to "fold" the beam path to reduce the mechanical length of the optical system, thereby allowing a physically compact system. In many cases, even a compact system can incorporate upwards of six mirrors and a comparable number of lenses all needing alignment so they are collinear. One of the major requirements for use of such systems in industry is a method of safe alignment. The alignment process requires that the aligner determine where the beam strikes each element. The aligner should also preferably be able to determine the shape or pattern of the laser beam at that point and its relative power. These alignments are further compounded in that the laser beams generated are not visible to the unaided human eye. Such beams are also often of relatively high power levels, and are thereby a significant hazard to the eyes of the aligner. Obvious an invisible beam makes it nearly impossible to align laser system without some form of optical assistance. The predominant method of visually aligning the laser beam delivery is the use of thermal paper, paper cards or fluorescing card material. The use of paper products which have limited power handling capability or coated plastics can produce significant debris and contaminants within the beam line that ultimately damage the optics. The use of the cards can also create significant laser light scatter jeopardizing the safety of the person aligning the system. This paper covers a new safety mirror design for use with at various UV and Near IR wavelengths (193 nm to 1064 nm) within laser beam delivery systems and how its use can

Electrical shielding box measurement of the negative hydrogen beam from Penning ion gauge ion source.

Science.gov (United States)

Wang, T; Yang, Z; Dong, P; long, J D; He, X Z; Wang, X; Zhang, K Z; Zhang, L W

2012-06-01

The cold-cathode Penning ion gauge (PIG) type ion source has been used for generation of negative hydrogen (H(-)) ions as the internal ion source of a compact cyclotron. A novel method called electrical shielding box dc beam measurement is described in this paper, and the beam intensity was measured under dc extraction inside an electrical shielding box. The results of the trajectory simulation and dc H(-) beam extraction measurement were presented. The effect of gas flow rate, magnetic field strength, arc current, and extraction voltage were also discussed. In conclusion, the dc H(-) beam current of about 4 mA from the PIG ion source with the puller voltage of 40 kV and arc current of 1.31 A was extrapolated from the measurement at low extraction dc voltages.

Inhibited-coupling HC-PCF based beam-delivery-system for high power green industrial lasers

Science.gov (United States)

Chafer, M.; Gorse, A.; Beaudou, B.; Lekiefs, Q.; Maurel, M.; Debord, B.; Gérôme, F.; Benabid, F.

2018-02-01

We report on an ultra-low loss Hollow-Core Photonic Crystal Fiber (HC-PCF) beam delivery system (GLO-GreenBDS) for high power ultra-short pulse lasers operating in the green spectral range (including 515 nm and 532 nm). The GLOBDS- Green combines ease-of-use, high laser-coupling efficiency, robustness and industrial compatible cabling. It comprises a pre-aligned laser-injection head, a sheath-cable protected HC-PCF and a modular fiber-output head. It enables fiber-core gas loading and evacuation in a hermetic fashion. A 5 m long GLO-BDS were demonstrated for a green short pulse laser with a transmission coefficient larger than 80%, and a laser output profile close to single-mode (M2 <1.3).

Across-arc versus along-arc Sr-Nd-Pb isotope variations in the Ecuadorian volcanic arc

Science.gov (United States)

Ancellin, Marie-Anne; Samaniego, Pablo; Vlastélic, Ivan; Nauret, François; Gannoun, Adbelmouhcine; Hidalgo, Silvana

2017-03-01

Previous studies of the Ecuadorian arc (1°N-2°S) have revealed across-arc geochemical trends that are consistent with a decrease in mantle melting and slab dehydration away from the trench. The aim of this work is to evaluate how these processes vary along the arc in response to small-scale changes in the age of the subducted plate, subduction angle, and continental crustal basement. We use an extensive database of 1437 samples containing 71 new analyses, of major and trace elements as well as Sr-Nd-Pb isotopes from Ecuadorian and South Colombian volcanic centers. Large geochemical variations are found to occur along the Ecuadorian arc, in particular along the front arc, which encompasses 99% and 71% of the total variations in 206Pb/204Pb and 87Sr/86Sr ratios of Quaternary Ecuadorian volcanics, respectively. The front arc volcanoes also show two major latitudinal trends: (1) the southward increase of 207Pb/204Pb and decrease of 143Nd/144Nd reflect more extensive crustal contamination of magma in the southern part (up to 14%); and (2) the increase of 206Pb/204Pb and decrease of Ba/Th away from ˜0.5°S result from the changing nature of metasomatism in the subarc mantle wedge with the aqueous fluid/siliceous slab melt ratio decreasing away from 0.5°S. Subduction of a younger and warmer oceanic crust in the Northern part of the arc might promote slab melting. Conversely, the subduction of a colder oceanic crust south of the Grijalva Fracture Zone and higher crustal assimilation lead to the reduction of slab contribution in southern part of the arc.

Polar cap arcs from the magnetosphere to the ionosphere: kinetic modelling and observations by Cluster and TIMED

Directory of Open Access Journals (Sweden)

R. Maggiolo

2012-02-01

Full Text Available On 1 April 2004 the GUVI imager onboard the TIMED spacecraft spots an isolated and elongated polar cap arc. About 20 min later, the Cluster satellites detect an isolated upflowing ion beam above the polar cap. Cluster observations show that the ions are accelerated upward by a quasi-stationary electric field. The field-aligned potential drop is estimated to about 700 V and the upflowing ions are accompanied by a tenuous population of isotropic protons with a temperature of about 500 eV. The magnetic footpoints of the ion outflows observed by Cluster are situated in the prolongation of the polar cap arc observed by TIMED GUVI. The upflowing ion beam and the polar cap arc may be different signatures of the same phenomenon, as suggested by a recent statistical study of polar cap ion beams using Cluster data. We use Cluster observations at high altitude as input to a quasi-stationary magnetosphere-ionosphere (MI coupling model. Using a Knight-type current-voltage relationship and the current continuity at the topside ionosphere, the model computes the energy spectrum of precipitating electrons at the top of the ionosphere corresponding to the generator electric field observed by Cluster. The MI coupling model provides a field-aligned potential drop in agreement with Cluster observations of upflowing ions and a spatial scale of the polar cap arc consistent with the optical observations by TIMED. The computed energy spectrum of the precipitating electrons is used as input to the Trans4 ionospheric transport code. This 1-D model, based on Boltzmann's kinetic formalism, takes into account ionospheric processes such as photoionization and electron/proton precipitation, and computes the optical and UV emissions due to precipitating electrons. The emission rates provided by the Trans4 code are compared to the optical observations by TIMED. They are similar in size and intensity. Data and modelling results are consistent with the scenario of quasi

SU-G-JeP3-06: Lower KV Image Dose Are Expected From a Limited-Angle Intra-Fractional Verification (LIVE) System for SBRT Treatments

Energy Technology Data Exchange (ETDEWEB)

Ding, G [Vanderbilt University Nashville, TN (United States); Yin, F; Ren, L [Duke University Medical Center, Durham, NC (United States)

2016-06-15

Purpose: In order to track the tumor movement for patient positioning verification during arc treatment delivery or in between 3D/IMRT beams for stereotactic body radiation therapy (SBRT), the limited-angle kV projections acquisition simultaneously during arc treatment delivery or in-between static treatment beams as the gantry moves to the next beam angle was proposed. The purpose of this study is to estimate additional imaging dose resulting from multiple tomosynthesis acquisitions in-between static treatment beams and to compare with that of a conventional kV-CBCT acquisition. Methods: kV imaging system integrated into Varian TrueBeam accelerators was modeled using EGSnrc Monte Carlo user code, BEAMnrc and DOSXYZnrc code was used in dose calculations. The simulated realistic kV beams from the Varian TrueBeam OBI 1.5 system were used to calculate dose to patient based on CT images. Organ doses were analyzed using DVHs. The imaging dose to patient resulting from realistic multiple tomosynthesis acquisitions with each 25–30 degree kV source rotation between 6 treatment beam gantry angles was studied. Results: For a typical lung SBRT treatment delivery much lower (20–50%) kV imaging doses from the sum of realistic six tomosynthesis acquisitions with each 25–30 degree x-ray source rotation between six treatment beam gantry angles were observed compared to that from a single CBCT image acquisition. Conclusion: This work indicates that the kV imaging in this proposed Limited-angle Intra-fractional Verification (LIVE) System for SBRT Treatments has a negligible imaging dose increase. It is worth to note that the MV imaging dose caused by MV projection acquisition in-between static beams in LIVE can be minimized by restricting the imaging to the target region and reducing the number of projections acquired. For arc treatments, MV imaging acquisition in LIVE does not add additional imaging dose as the MV images are acquired from treatment beams directly during the

Elaboration of metallic and composite fillings by plasma transferred arc. Process analysis and tribological study